Archive for January, 2007
by Elizabeth Serai James
jphpk.gov.my
KUCHING - The new approach to the management of sustainable harvest of the Black-nest swiflets at Niah National Park has been a success after two years of implementation.
The chief technical adviser for Danish International Development Assistance (DANIDA)/Support to Wildlife Master Plan Implementation (SWMPI) Project, Julian T Inglis, disclosed this in an interview with Tribune at his office yesterday.
Niah Cave used to be a major source of the ‘black’ edible bird’s nests produced by the Blacknest Swiflets (Aerodramus maximus) in the 80s. However, the swiflets population had declined tremendously over the past few decades, he said.
According to the DANIDA/SWMPI census in 2002, 65,000 bird’s nests were found in Niah Cave compared to 1,700,000 nests found in the first census carried out by Banks in 1935, a decrease of about 96 percent.
Inglis pointed out that a species that had apparently withstood traditional exploitation for more than a century was diminishing at an alarming rate simply because of uncontrollable and indiscriminate harvesting practices carried out in recent years.
He said: “In addition, weak management or lack of initiatives from the licensees, rampant poaching as well as disputes over ownership claims and disunity among the local communities worsened the situation.”
Responding to widespread concerns, the State government took a drastic measure to ban all nest harvesting activities at Niah National Park in April 1989 and extended the ban for another four years in 1992. However, by 1996, it was clear that the ban was not effective, noted Inglis.
The ban was lifted in 1997 with the management of nest-yielding caves reverting to the licensees. But the approach did not improve the situation either, he said, adding that both measures to save the Black-nest swiflets had failed.
According to Inglis, there was also no proper management and regulation in the Cave which led to the accumulation of rubbish over the years, graffiti on cave walls, illegal immigrants working in caves, nest poaching, gambling, drug abuse by workers and noise such as loud music.
He stressed that the previous measures failed because the influential role of the bird’s nest traders who controlled the industry was not recognised and they had no sense of ‘ownership’.
However, under the new management approach a comprehensive study was drawn up on the breeding biology of the Black-nest swiflets at the Cave.
He explained: “The new approach, implemented two years ago, is acceptable to the State government as well as the local community. Under the approach, harvesting of nests is not allowed four months in a year.
“After four months, licensees are allowed to harvest every month.”
He pointed out that “it takes an average of 30 days for each pair of Black-nest swiflet to lay one egg and it will take another 25 days to incubate one egg. A baby bird needs at least 45 days to grow big. Thus, it takes four months for the young birds to mature.”
The breeding cycle of Black-nest swiflets - from its ability to fly to building its own nest - is about one year, explained Inglis.
The date for the “closing of Niah Cave from harvesting activity” is recommended by the Forestry Department through dialogues held with the local communities.
“Within that time, the Cave will be guarded by Cave guards and bird’s nests traders will give loans to their workers as compensation for the four-month inactivity during which they are not allowed to harvest,” said Inglis.
Last year, the closure of the Cave was from February 1 to May 23; this year the closure is from January 1 to May 1.
He said by the time the Cave was reopened for harvesting activity, the nests would be “fully matured”, enhancing the quantity of the harvest.
According to DANIDA/SWMPI project community adviser, Dr Lim Chan Koon, the Black-nest swiflet is the only species of commercial value in Niah Cave.
Lim said apart from the management plan, the new approach was to work together with the local communities and stakeholders.
“We hold dialogues and gatherings with all the stakeholders. The stakeholders are the licensees, the bird’s nest traders, the cave guards and cottage bird’s nest processors and the Forestry Department,” said Lim.
According to him, some of the bird’s nests are sold locally. Most, however, are exported to Hong Kong and Singapore.
He said: “One kg of freshly-collected bird’s nests can fetch between RM900 and RM1500, depending on the quality. There is a huge demand for the commodity.”
January 31st, 2007
Dietmar Gundacker, Sally P. Leys2, Heinz C. Schröder, Isabel M. Müller and Werner E.G. Müller1
Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universität, Duesbergweg 6, D-55099 Mainz, Germany, and 2Department of Biology, University of Victoria, British Columbia V8W 3N5, Canada
Among the sponges (Porifera), the oldest group of metazoans in phylogenetic terms, the Hexactinellida is considered to have diverged earliest from the two other sponge classes, the Demospongiae and Calcarea. The Hexactinellida are unusual among all Metazoa in possessing mostly syncytial rather than cellular tissues. Here we describe the purification of a cell adhesion molecule with a size of 34 kDa (in its native form; 24 kDa after deglycosylation) from the hexactinellid sponge Aphrocallistes vastus. This adhesion molecule was previously found to agglutinate preserved cells and membranes in a non–species-specific manner (Müller, W. E. G., Zahn, R. K, Conrad, J., Kurelec, B., and Uhlenbruck, G. [1984] Cell adhesion molecules in the haxactinellid Aphrocallistes vastus: species-unspecific aggregationfactor. Differentiation, 26, 30–35). The fact that the aggregation process required Ca2+ and was inhibited by bird’s nest glycoprotein and D-galactose but not by D-mannose or N-acetyl-D-galactosamine suggests that this cell adhesion molecule is a C-type lectin. To test this assumption, two highly similar C-type lectins were cloned from A.vastus. The deduced polypeptides of the two cDNA species isolated classified these molecules as C-type lectins. The calculated Mr of the 191 aa long sequences were 22,022 and 22,064, respectively. The C-type lectins showed highest similarity to C-type lectins (type-II membrane proteins) from higher metazoan phyla; these molecules are absent in non-Metazoa. The two sponge C-type lectins contain the conserved domains known from other C-type lectins (e.g., disulfide bonds, the amino acids known to be involved in Ca2+-binding, as well as the amino acids involved in the specificity of binding to D-galactose) and a hydrophobic N-terminal region. The N-terminal part of the purified C-type lectin was identical with the corresponding region of the deduced polypeptide from the cDNA. It is proposed that the A.vastus lectins might bind to the cell membrane by their hydrophobic segment and might interact with carbohydrate units on the surface of the other cells/syncytia.
Key words: sponges/Hexactinellida/Aphrocallistes vastus/aggregation factor/lectin/C-type lectin/evolution/cell adhesion
Introduction
Multicellularity has arisen several times in evolution and in all major kingdoms (prokaryotes, plants, fungi, and animals; Schopf, 1993). It is generally agreed that multicellular plants, the red algae, the brown algae, the land plants and the fungi arose separately from unicellular ancestors (Devereux et al., 1990; Kirk, 1997). Molecular (Müller, 1995) and morphological (Müller, 1997; Wimmer et al., 1999) data indicate that the transition from the Protozoa to the Metazoa occurred only once in evolution. Sequence data from a variety of proteins involved in cell–cell interactions indicate that all animals, including sponges, are of monophyletic origin (Müller, 1995).
The phylum Porifera, the oldest group of multicellular animals, includes three classes: the Demospongiae, the Calcarea, and the Hexactinellida. The Hexactinellida differ substantially from the other two sponge classes in having largely syncytial tissues (Reiswig, 1979; Mackie and Singla, 1983; Leys, 1995, 1999). The majority (75%) of the sponge constitutes a multinucleated syncytium; the remaining portions of the sponge function independently as cells but are still connected to the whole by open or plugged cytoplasmic bridges (Leys, 1999). Knowledge of hexactinellid embryology is still very limited, as for the most part these sponges inhabit deep waters accessible only by submersible or dredge. Early descriptions of hexactinellid embryos obtained from dredged specimens (Ijima, 1901; Okada, 1928) and an examination of embryos from a population of hexactinellids recently discovered (Boury-Esnault et al., 1999) suggest that the embryo is “cellular” but that the larva is clearly syncytial. How the syncytial tissue arises remains unclear.
Two alternative hypotheses have been proposed to explain relationships between the major sponge classes. One suggests that the Demospongiae are more closely related to Hexactinellida based on presumed larval similarities (Böger, 1988). The other divides the Porifera into the adelphotaxa of the Hexactinellida and the Demospongiae/Calcarea based on the gross difference in tissue structure (Reiswig and Mackie, 1983; Leys, 1999). Recent molecular evidence supports the latter view (Koziol et al., 1997; Kruse et al., 1998; Skorokhod et al., 1999) suggesting that Calcarea are most closely related to other diploblasts and form a clade with the Demospongiae. The Hexactinellida are thought to have diverged first from a common ancestor of the Metazoa (Müller et al., 1998; Müller and Müller, 1999).
There is now a wealth of cellular and molecular evidence to suggest that the Demospongiae have many of the features characteristic of much evolutionarily younger metazoan taxa (e.g., the receptor tyrosine kinases (Müller and Schäcke, 1996), integrins (Pancer et al., 1997; Wimmer et al., 1999), collagen (Exposito et al., 1991), and the metabotropic glutamate/GABA-like receptor (Perovic et al., 1999)).
The role of the aggregation factor (AF) in sponges has been studied in detail (reviewed in MĂĽller, 1982, and FernĂ ndez-Busquets and Burger, 1999). The AF isolated from demosponges has been shown to function in a species-specific manner (Moscona, 1968; MĂĽller et al., 1979a). Furthermore, in the Demospongiae a lectin belonging to the S-type lectins (Pfeifer et al., 1993) has been found to be involved in a species-specific aggregation complex (Wagner-HĂĽlsmann et al., 1996). A similar “factor” isolated from the hexactinellid Aphrocallistes vastus aggregated cells in the presence of Ca2+ non-species-specifically (MĂĽller et al., 1984). The preparation contained several fractions with one dominant protein species of 34,000 kDa. Sugar analysis revealed that the A. vastus AF was a glycoprotein consisting of 55% (w/w) protein, 40% neutral carbohydrate and 2% hexuronic acid (MĂĽller et al., 1984). The experiments also showed that the A. vastus AF “agglutinated” the cells by interacting in a homo- or heterophilic manner of the second order.
Until now no cell adhesion molecules have been cloned from hexactinellid sponges. However, the syncytial nature of hexactinellid tissue, namely, its ability to fuse to form a syncytium after dissociation through fine mesh, and the evidence that hexactinellid sponges may have been the earliest multicellular animals to have evolved on earth, suggest that a study of cell adhesion molecules in hexactinellid sponges may reveal new mechanisms of cell–cell recognition within the Metazoa.
In the present study, the previously isolated AF was purified and shown to have a size of 34 kDa (24 kDa after deglycosylation). The factor caused aggregation in the presence of Ca2+ and this function was inhibited by D-galactose. These properties—Ca2+-dependency and sugar specificity—suggest that the previously termed AF is in fact a Ca2+-dependent lectin. To test this assumption, two highly similar Ca2+-dependent lectins (C-type lectin) have been cloned from A.vastus. Phylogenetic analysis revealed that the cloned putative C-type lectin represents the oldest (phylogenetic) member of this class within the Metazoa.
The sequences reported here are deposited in the EMBL/GenBank data base under the accession no. AJ276450 (APHRLECC1) and AJ276451 (APHRLECC2) as Aphrocallistes vastus C-type lectins.
Results
Aggregation-promoting activity of an extract from A.vastus
It was previously found that the partially enriched fraction of the A.vastus extract (formerly termed AF) caused aggregation of preserved cells and syncytia at Ca2+ concentrations greater than 1 mM (Müller et al., 1984). By applying the enrichment procedure described previously, aggregates larger than 500 µm diameter (Figure 1B,C) were obtained from single cells/membranes (Figure 1A). The size of the aggregates increased with increasing concentration of the extract: at 5 units of extract the diameter of aggregates was approximately 500 µm (Figure 1B); at 20 units of extract they were larger than 4 mm (Figure 1 C).
January 30th, 2007
web.uct.ac.za
J.A. Harrison
ADU, UCT, Rondebosch, 7701
While scanning old issues of Ostrich, I was struck by the photograph on the next page which shows a large colony of South African Cliff Swallow Hirundo spilodera nests on the walls of a building. I had never come across this type of nest site in this species before, and the fact that it was a man-made structure, but different to the culverts and bridges normally used, pricked my interest. The structure is an old mill building on the farm Wheatlands in the Graaff- Reinet district and it is reported to have been colonized continuously from 1896 to the year of writing, 1940 (Taylor 1942). Further investigation led me to an article by none other than Austin Roberts (1939), who gave the following account of cliff swallows nesting on buildings:
‘By far the commonest of the Swallows in the Union is the Cliff Swallow, which formerly nested in large communities under overhanging rocks or earth banks on rivers, but had found the eaves of buildings, bridges, railway water tanks and the like so much suited to it that it has increased enormously in numbers in recent years. In the early ‘nineties (That’s the 1890s! - Ed.) it nested in great numbers under the eaves of the ‘Gereformeerde’ church at Potchefstroom and also on some farm houses in the neighbourhood. More recently a great controversy raged in the local newspaper, owing to the local fire brigade having been used to turn the hoses on the nests to wash them away! The church community at Strydenburg, C.P., solved the problem of keeping away these Swallows from building under the eaves of the church and causing much trouble by the mess they made, by erecting fine wirenetting wherever they were likely to build their nests. Such favoured nesting sites are not confined to churches and large public buildings, but also private residences in towns in many cases - if they are tolerated.’
Other accounts of SA Cliff Swallows using occupied buildings were found in Godfrey (1943), Winterbottom (1962) and Rowan (1963), but these, plus the two accounts cited above, all referred to old records from years spanning 1879 to 1940. As in the quote above, these also refer to vigorous efforts made to deter the birds from nesting on buildings, because of the mess and the parasites that accompanied them. They generally give an impression of the birds being resilient and difficult to dissuade.
My curiosity now thoroughly aroused, I canvassed the wealth of experience and first-hand knowledge available through the internet interest group, SABIRDNET (sabirdnet@unp.ac.za). I asked for information on any South African Cliff Swallow nest sites which are not situated on bridges or culverts. These are the responses received:
Mike Pope (Mpope@Maven.co.za): I live in Midrand where there are three separate Cliff Swallow colonies. Two are under large stormwater drains which are under two really busy roads, and the last is under the eaves of an abandoned cattle kraal in an open grassland.
Dr Pete Irons (pirons@op1.up.ac.za): In 1990 near Ramathlabama on the South African-Botswana border, there was a small colony nesting in an old farm building with a flat roof. The number of birds involved was not more than about 20-30. It was a flat area in bushveld habitat, without much suitable topography or structures for nest sites in the area.
Dr Hamish Campbell (finfoot@icon.co.za): In September 1987, Johann Knobel took me for a weekend to Barberspan. Here we saw hundreds of SA Cliff Swallows roosting in a deserted and disintegrating corrugated iron hangar which, I presume, had served an ancient airstrip there.
Stephan Terblanche (sterblanche@mailhub.cpro.co.za): I recall seeing Cliff Swallow nests at Barberspan, on the north-western side of the pan, in about 1995. They were under the roof of a large corrugated-iron barn, which had open sides.
David Allan (DavidA@prcsu.durban.gov.za): I saw SA Cliff Swallows breeding under overhangs on Ecca sandstone cliffs at Bald Ibis breeding colonies in Mpumalanga Province years ago. I have one record of this for the Bald Ibis colony on the farm Buhrmansklipkrans (2630CAC); on 30/9/1982 I recorded c. 15 birds at nests, and on 29/10/1982 hundreds of birds at active nests. I also recorded a colony at Barberspan (2625DAA) on 3/2/1983 when there were c. 40 active nests under an isolated concrete structure in the middle of the pan.
Shaun Peard (desel@iafrica.com): I recently saw a colony of SA Cliff Swallows nesting under the eaves of an old dressed stone building about 20Ăżkm south of Dordrecht on the Queenstown-Dordrecht road. There must have been in excess of 70 nests. The building appeared to be still used as a trading store and was about 30Ăżm off the edge of this busy road.
Paul Martin (apmartin@global.co.za): The colony in Dordrecht, reported by Shaun Peard, has been in existence for many years and is the most unusual nest site I have seen. They nest rather like House Martins at this venue. Bob Cullen (rc36@mweb.co.za): On 2 May 1993, during a visit to Suikerbosrand Nature Reserve near Heidelberg, Gauteng, I noted that SA Cliff Swallows appeared to be nesting in the main Administration Block there. This is not certain because, although they were disappearing under the eaves, I couldn’t actually see the nests from the road.
Dr Alan Kemp (kemp@tm.up.ac.za) and Andrew Tucker (S9604547@op1.up.ac.za): SA Cliff Swallows nest under the main gate to the CSIR, Pretoria, which is rather bridge-like. At least during 1970-74, they nested under the eaves of a silo on the University of Pretoria Proefplaas, just across the road from the CSIR (and may still do); the latter colony may have sprung from the CSIR one. Otherwise I know only bridges (e.g. Witbank N4, a huge core colony for many years since construction of the N4, which has spread to several neighbouring bridges only this decade).
Dieter Oschadleus (dieter@adu.uct.ac.za): Cliff Swallows bred on the buildings of the CSIR, Pretoria, for many years. Burgerjon (1964) conducted a breeding study on these colonies from 1958 to 1961. When I worked at the CSIR as a student in the December holidays of 1985 to 1988, I recall seeing the swallows breeding on the buildings. To prevent the swallows from breeding, netting was being put in front of the entire Nuclear Physics building of several floors height!
I spent the next year in the army and returned to work at the CSIR in 1990. I’m not sure if the swallows were still breeding on the buildings at that time. From January 1995 to September 1997 I kept a weekly species list of the waterbirds at the CSIR. Cliff Swallows were seen drinking water from the main dam (Oschadleus 1995), but I did not record breeding activity. From my (untrustworthy?) memory the swallows were only breeding in a fair-sized colony on the A-frame entrance gate, with possibly an occasional attempt on some of the CSIR buildings. From March 1996 to September 1997 I kept a monthly species list of the all CSIR birds. Cliff Swallows were present in August 1996 to February 1997 and in September 1997. The swallows definitely bred on the A-frame gate in the summers of 1996/97 and 1997/98.
The netting (possibly applied for a few years in the late 1980s) seems to have resulted in the swallows moving their colony to the A-frame gate. This causes a mess of droppings, feathers and occasional dead chicks on the road leading into the CSIR. The site maintenance team considered destroying the site but staff resisted the idea. Now the nests are cleared away after breeding is completed and the birds have migrated. In contrast, Little Swifts Apus affinis have bred on the CSIR buildings (Nuclear Physics and many others), probably every year and certainly the last five years. Although they would have been excluded from some nesting sites by the netting, they can breed on more inaccessible sites. They also seem to breed in smaller colonies scattered throughout the CSIR, making any attempts to eradicate them impractical.
Martin Kerr (martin.kerr@eskom.co.za): Alan Kemp mentioned the colonies of swallow nests under the bridges across the Pretoria-Witbank highway N4. When we first travelled that road back in 1978/79, I noticed that all the nests were on the exit sides of both lanes, on the opposite side to the oncoming traffic. More recently the nests have spread to both entry and exit sides of the bridges and I wondered what caused the change. Other puzzling facts are that not all the bridges have nests on them, and there are far fewer bridges across the Witbank-Johannesburg highway that have nests on them. The design of the bridges could be a factor.
Dr Pieter van Eeden (PieterVE@erlab.erwat.co.za): I am the pollution ecologist for East Rand Water Care Co. and we have a wastewater treatment plant (WWTP) in Olifantsfontein, between Kempton Park and Midrand. A relatively new second-phase treatment plant was not put into use owing to technical problems, but was kept filled with water to prevent cracks from forming. Concrete bridges cross over and around the sides of the aeration chambers to get to the aerators. Under these walkways, I saw many active nests with SA Cliff Swallows flying to and from them.
Derek Solomon (osi@internet.co.zw): I know of no records of SA Cliff Swallows in the Matobo Hills, near Bulawayo in Zimbabwe. (The Matobo Hills could be considered a suitable natural site for cliff swallows to nest at because of the extensive granite cliffs. - Ed.) They were recorded breeding in a culvert over a road outside Bulawayo many years ago, then disappeared. The records in ASAB2 are for a small colony that appeared out of the blue during that period - just outside the village of Headlands, and I ringed some of these birds. Unfortunately the site is very exposed and the nests were vandalized on several occasions. As far as I know no birds returned to this site last year. These are the only known breeding records for this species in Zimbabwe.
Burke Korol burke.korol@sk.sympatico.ca: The cliff swallows Petrochelidon pyrrhonata here in Canada often use buildings and bridges for nesting, but they still use rock faces when they are available. Just last year I found a couple of colonies in British Columbia, with 25 and 75 nests each. (Prior to being placed in the genus Hirundo, the SA Cliff Swallow was considered to belong to the genus Petrochelidon. - Ed.) Add to these the findings of Dr Roy EarlĂ© who did an intensive study of the species in the Free State in the 1980s. He found only a few ‘natural’ breeding sites, these all being in man-made quarries. All the colonies in the Free State were ‘distant from human habitation and no colonies were located in barns or any other structures occupied by humans’ (EarlĂ© 1985).
From all of this I think one can draw a number of conclusions:
SA Cliff Swallows have been using man-made structures as nest sites for at least 120 years, possibly considerably longer.
The first 60 years of this historical period appear to have been characterized by the birds’ use of a wide range of man-made structures, including bridges, water towers, churches, brick-and-stone residences, and African huts (Godfrey 1943). In most cases this met with vigorous attempts to discourage colonization of buildings and to destroy existing colonies.
Since this early period, there has clearly been a marked shift in, or perhaps only a narrowing of, the choice of man-made sites, so that now the overwhelming majority of nest sites are located under bridges and culverts, or on other concrete structures which resemble these. Although many of these sites are over water, the presence of water does not appear to be a determining factor (Earlé 1985).
Some breeding colonies still use occupied buildings, natural and semi- natural sites, but this is rare.
The breeding range of the SA Cliff Swallow is largely restricted to the grassland biome and the adjacent grassy eastern parts of the Nama Karoo in South Africa. It is interesting to note that its abundance is not nearly as great in highland sour grasslands as in lowland sweet grasslands (ASAB2). It is reasonable to assume that this is approximately representative of the original distribution before human colonization, and that breeding sites would therefore have been restricted to sparsely scattered rocky outcrops and hills, and to suitable earthen banks along watercourses.
In various accounts it is stated that the range and abundance of the SA Cliff Swallow have undergone a number of significant fluctuations, with the implication that expansions may be causally linked to adaptation to new breeding sites, and contractions to persecution at those sites (e.g. Roberts 1939; Godfrey 1943; Rowan 1963). Given that these swallows forage over open, grassy habitats near to their breeding colonies (Roberts; ASAB2), and that they are highly social, it is clear that breeding sites are an important factor in distribution. The development of a modern road network is a relatively recent, post-war phenomenon, seeming to correlate fairly well with the end of the period during which buildings were used on a large scale by the swallows. The numerous new bridges and culverts must have provided a superabundance of suitable and relatively safe nesting sites - good alternatives to either natural sites or buildings. The range of the bird corresponds well with areas of intense development where such roads were built first; as modern roads extended into relatively remote rural areas, the species was given the opportunity to expand its range (e.g. Brooke 1959; Winterbottom 1959).
I find it remarkable that virtually the entire population of a species can make not one but two radical changes in its breeding behaviour in the space of a century or so. The plasticity of bird behaviour is a fascinating field of enquiry which forces one to consider the issue of ‘culture’ in wild populations. How are changes in behaviour initiated? How are new ideas transmitted? What determines whether a particular behaviour spreads and becomes entrenched, or remains unstable and changeable? How are choices between old and new ways made? Surely the SA Cliff Swallow must offer unusually good opportunities to investigate some of these questions.
References
Burgerjon, J.J. 1964. Some census notes on a colony of South African Cliff Swallows Petrochelidon spilodera (Sundevall). Ostrich 35: 77-85.
Brooke, R.K. 1959. Avian highlights of a journey across southern Africa. Ostrich 30: 82-83.
Earlé, R.A. 1985. The biology of the South African Cliff Swallow Hirundo spilodera. PhD thesis, Rhodes University.
Earlé, R.A. 1986. The breeding biology of the South African Cliff Swallow. Ostrich 57: 138-156.
Godfrey, R. 1943. The South African Cliff Swallow. Ostrich 14: 219-226.
Oschadleus, H.D. 1995. Swift and swallow drinking patterns. Laniarius 56: 26. [Also reprinted in Birding in Southern Africa 47(2): 49.] Roberts, A. 1939. Swifts and other birds nesting in buildings. Ostrich 10: 85-99.
Rowan, M.K. 1963. Range of the Cliff Swallow. Ostrich 34: 181-182.
Taylor, J.S. 1942. Notes on the martins, swallows and swifts: Graaff-Reinet. Ostrich 13: 148-156.
Winterbottom, J.M. 1959. Range of the cliff swallow. Ostrich 30: 87.
Winterbottom, J.M. 1962. Some manuscript notes of S.F. Townsend for the period 1878-1925. Ostrich 33:66-71.
January 29th, 2007
sciencedaily.com
Science Daily — ITHACA, N.Y. — Billing and cooing in an old and familiar love nest doubles and even triples some birds’ chances of producing progeny, researchers at Cornell University have discovered. Their study, which focused on Japanese quail, is the first to document what farmers and researchers have long suspected: that breeding is often more successful when animals mate where they have mated before. In this study, the inseminations were more likely to fertilize eggs when they occurred in cages where the birds had previously encountered birds of the opposite sex.
“We now know that fertilization isn’t just a matter of plumbing; there’s a lot of strategic decision-making going on that is regulated by the brain in response to the social and physical environment,” says Elizabeth Adkins-Regan, a professor in the departments of psychology and of neurobiology and behavior at Cornell.
“Pavlovian conditioning has long been assumed to be adaptive. This study is the strongest evidence yet that Pavlovian sexual conditioning increases the reproductive success of animals, both male and female,” she says.
In Pavlovian sexual conditioning, external cues allow anticipation of mating and lead to improvements in mating behavior. This study shows that the conditioning contributes to successful fertilization and not simply successful mating.
The study, conducted with Emiko A. MacKillop, Cornell ‘02, a former Cornell research assistant now in graduate school at the State University of New York in Binghamton, is published online at The Royal Society Web site and will be published in print, in the society’s Proceedings: Biological Sciences on Aug. 22. The Royal Society is an independent United Kingdom academy promoting the natural and applied sciences.
The Cornell researchers put 26 male Japanese quail, a species already well established in neuroendocrine research, with females in two sets of cages. In one set, the males had mated with females before, but they had not previously encountered a female in the second set of cages. The researchers were able to document how often the females were fertilized in both situations.
“We found that inseminations fertilized at least one egg twice as often in cages where the males had been placed with females previously, compared with matings in cages where the males had not previously hosted a female,” says Adkins-Regan.
To test the females, the same experiment was conducted with the sexes reversed. The rate of eggs fertilized was three times greater in cages where the females had previously been exposed to males, compared with those in cages where they had not previously encountered males.
The findings could be relevant for breeding endangered species as well as farm animals. “Pavlovian conditioning is a universal property of nervous systems,” says Adkins-Regan. “It is likely, therefore, also to be relevant to fertilization success for wild animals in natural mating systems.”
The research was supported, in part, by the National Science Foundation.
Related Links:
o Elizabeth Adkins-Regan: http://www2.psych.cornell.edu/regan/
o The Royal Society: http://www.pubs.royalsoc.ac.uk/biol_lett/biol_lett_main.htm
Note: This story has been adapted from a news release issued by Cornell University News Service.
January 26th, 2007
sciencedaily.com
Science Daily — ITHACA, N.Y. — Earlier springs with warmer temperatures over the past 30 years have prompted a ubiquitous North American bird species, tree swallows, to begin laying eggs, on average, a week or more earlier. But whether these harbingers of global warming are being adversely affected by changing weather patterns isn’t clear, biologists in New York, Wisconsin and California report in Proceedings of the National Academy of Science (PNAS ).
When tree swallows start earlier, they often lay more eggs, say the biologists, referring to data collected by thousands of volunteer citizen-scientists who have watched the birds’ nest boxes for 40 years.
“We don’t know whether earlier lay dates and larger clutch sizes will be good in the long term for populations of tree swallows,” says David W. Winkler, a Cornell University professor of ecology and evolutionary biology. “And tree swallows are just one of the many organisms that potentially can be affected by climate change.”
After an exhaustive, three-year statistical analysis of bird and weather data, Winkler, Peter O. Dunn of the University of Wisconsin-Milwaukee and Charles E. McCulloch, a biostatistician at the University of California-San Francisco, report the effects of climate change on swallows in the PNAS Online Early Edition, week of Sept. 23, 2002. Their article is titled “Predicting the effects of climate change on avian life history traits.”
Tree swallows (Tachycineta bicolor ) are astute weather monitors, Winkler explains, because of three characteristics:
o They are aerial insectivores, hunting the insects they crave “on the wing.” (An adult tree swallow can capture as many as 50 insects before returning to the nest and feeding its young.)
o Tree swallows are “income breeders” that rely, more than many other species, on their daily foraging intake — both before and during the spring breeding season. (Tree swallows begin breeding once their source of insect income looks large enough, but the future of their growing family is at the mercy of sometimes-fickle weather.)o Insects the swallows need do not fly during cool weather, and swallows will not forage on the ground. (A sudden cold snap and a local shortage of insects can kill 5- to 8-day-old nestlings before their developing bodies learn to thermoregulate and grow insulating feathers. When adult tree swallows are forced by cool weather to travel greater distances in search of insects, they may be forced to abandon their chicks.)
Professional ornithologists rely on trained amateurs in volunteer programs, such as the Cornell Lab of Ornithology’s Nest Record Card Program, to report on birds throughout a wide geographic area. In 1999, after studying 21,000 nest records from Cornell’s database and similar programs in Canada, Dunn and Winkler reported that the lay date of tree swallows shifted an average of nine days earlier between 1959 and 1991.
Since that report, which was among the first to link animal-behavior changes to global warming, Winkler and Dunn have worked with McCulloch and extended the analysis to another key life-history trait — the number of eggs birds lay each year.
January 25th, 2007
home.intekom.com
The Blue Swallow is an ambassador for a vital South African ecosystem namely grasslands. The South African grasslands form the major portion of our water catchment areas. More than 60% of the Grassland Biome has already been modified - forestry and agriculture playing largest roles. In South Africa only 2,23% of the Grassland Biome is formally conserved. The Grassland Biome is the least conserved, most transformed and therefore most highly threatened of South Africa’s 7 biomes.
The people of South Africa and the Blue Swallows are equally dependent upon the good management of the grasslands as “water factories”. The Blue Swallow is specialised to living in two grassland types in South Africa namely North-Eastern Mountain Sourveld and Natal Mist Belt. Of all the grassland types in South Africa in need of conservation, the two highest priority types are North-Eastern Mountain Sourveld and Natal Mist Belt. Both grassland types are located along the eastern South African escarpment in the Northern Province, Mpumalanga and KwaZulu-Natal.
As a globally threatened species the Blue Swallow, as a component of its unique grassland ecosystems in South Africa and Africa, should be viewed as the ambassador for the conservation of all of the other faunal and floral components and processes of its unique grassland ecosystem. Conserving the Blue Swallow will therefore result in the survival of other unique grassland species for which there is no working group and thus no conservation efforts.
South Africa is world-renowned for its biodiversity. Our grasslands are amongst the richest habitats for this biodiversity and are home to many fascinating endemic bird species, bird species only found in South Africa and nowhere else in the world. Birding is the fastest growing recreational activity in the world. The effective conservation of our bird-life will maintain unique birding areas that foreign tourists will visit and from which local communities will benefit. Protection of South Africa’s high biodiversity systems will be good for biodiversity, good for water quantity and quality, provide tangible benefits to local communities and be good for the Blue Swallow.
Current Conservation Status
The Blue Swallow is considered to be South Africa’s most endangered bird species (Brooke 1984). There are currently 81 known nests and a further 39 possible nests in South Africa and Swaziland. The numbers were obtained after extensive surveys conducted over the past fourteen years. Optimistically it may be possible to add a further ten nests once certain localities in the former Transkei and certain of the tribal trust-land areas in KwaZulu-Natal have been investigated for the presence of Blue Swallows.
An assessment for the total African distribution range of the Blue Swallow in 1985 listed it as near-threatened. By 1994 the Blue Swallow’s status had deteriorated and it is currently considered to be vulnerable (Collar & Stuart 1985, Collar et al. 1994). Since the 1994 assessment at least for South Africa and Kenya the species status has probably deteriorated from vulnerable to endangered (Nasirwa & Njoroge 1996). Countries for which information is minimal at this stage are the Democratic Republic of Congo, Zambia and Mozambique.
As a species of high conservation priority the Blue Swallow, as a component of its unique grassland ecosystems in South Africa and Africa, should be viewed as the ambassador for the conservation of all of the other faunal and floral components and the processes of its preferred grassland ecosystems. The Blue Swallow therefore ensures the long-term survival of other grassland species for which there is no working group and thus no conservation efforts.
Current global population
An optimistic assessment indicates that there are only 1500 breeding pairs of Blue Swallows remaining for their entire African breeding distribution range. The adult breeding population total is approximately 3 000 individuals.
A total of 89 definite and 34 possible breeding pairs are thought to occur in Southern Africa. An estimated 20 breeding pairs occur in Swaziland. In South Africa KwaZulu-Natal contains 51 definite and a further 19 possible nests, Mpumalanga contains 27 definite and a further 3 possible nests and the Northern Province contains 1 definite and a further 2 possible nests.
Elsewhere in Africa, numbers of breeding birds are estimated as follows: 300 pairs in the eastern-highlands of Zimbabwe, with another 100 pairs possible in adjacent Mozambique; 360 pairs in Malawi; 400 pairs in the southern highlands of Tanzania and 100 pairs in each of northeastern Zambia and southeastern Democratic Republic of Congo (DRC), respectively.
Large breeding populations of Blue Swallows currently in protected areas are Nyanga National Park (580 km²) in Zimbabwe (estimate of 200 breeding pairs) and Nyika National Park (3134 km²) in Malawi (conservative estimate of 260 breeding pairs) (Worsley pers comm., Holroyd & Quinni in prep).
Distribution range
The Blue Swallow’s global distribution range is limited to 10 countries in sub-Saharan Africa and is subsequently an intra-African migrant (Turner 1989). It breeds in KwaZulu-Natal, Swaziland, Mpumalanga, Northern Province, eastern Zimbabwe and adjacent Mozambique in southern Africa. In east Africa the Blue Swallow breeds in Malawi, north-eastern Zambia, south-eastern part of Democratic Republic of Congo and south-western Tanzania (Turner 1989). The birds arrive at their breeding grounds in South Africa and Swaziland towards the end of September (Parker 1994), and depart again in mid-April (Keith et al. 1992). From throughout their breeding range the Blue Swallows migrate in the non-breeding season to Uganda, western Kenya, north-eastern part of Democratic Republic of Congo and possibly also north-western Tanzania in central Africa but do not breed there (Earle 1987).
The furthest north that a Blue Swallow has ever been recorded is Kidepo Valley National Park that has its north-western boundary on the border between Uganda and Sudan in the north-eastern part of Uganda (Butchard 1996). The Blue Swallow range states are Democratic Republic of Congo, Uganda, Kenya, Tanzania, Malawi, Zambia, Zimbabwe, Mozambique, South Africa and Swaziland.
Habitat
The Blue Swallow prefers high altitude, high rainfall (> 1000 mm p.a.), undulating, open, primary mist-belt grasslands (Allan et al. 1988). The preferred sour grasslands generally have a sward height of < 0.5 meters. The Blue Swallow ecosystem throughout its breeding range in Africa is characterised by the occurrence of mist, during the birds breeding periods. In South Africa and Swaziland the bird is specialised to and therefore only found within the two grassland types known as north-eastern mountain sourveld and Natal Mist-Belt (Acocks 1975). Natal Mist-Belt is the grassland type in which the Blue Swallow is found at the southernmost limit of its African distribution range - KwaZulu-Natal in South Africa. From information published in 1967 the grassland type in which the Blue Swallow is found in Zimbabwe, Mozambique, Malawi and Zambia appears to be similar to the grassland type known as North-Eastern Mountain Sourveld in South Africa and Swaziland (Wild et al. 1967). At this stage the grassland type in which the birds are breeding in Tanzania and the Democratic Republic of Congo is believed to be similar to that of their range in Zimbabwe, Mozambique, Malawi and Zambia. As yet no information could be obtained on the grassland composition or type that the birds inhabit in north-western Tanzania. In South Africa North-Eastern Mountain Sourveld contains 130 endemic plant species and Natal Mist-Belt contains 51 endemic plant species.
The two grassland types in urgent need of conservation in South Africa are North-Eastern Mountain Sourveld and Natal Mist Belt (Duthie 1994; Low & Rebelo 1996).
Nest, Eggs and Nestlings
Blue Swallows construct a cup-shaped nest out of a mixture of mud and grass. The nest is attached to the wall of natural or artificial holes. Natural holes currently used by the birds are natural sinkholes and Aardvark burrows or artificial sites such as abandoned mine shafts. The birds prefer holes with an overhang under which the nest is constructed so as to protect the exposed cup from the wind and rain. Nests in suitable nest sites are often repaired each breeding season and used over many seasons. Both the male and female contribute to nest building or repair. The female carrying out most of the work.
Two to three eggs are laid at 24 to 48 hours between each successive egg. Only the female incubates the eggs for 14 - 16 days. The female incubates the nestlings. Both the male and female feed the nestlings. At the peak of their development the adult birds arrive at the nest with food for the nestlings at a rate of once every 2 minutes. Nestlings fledge 20 to 24 days after hatching and remain in the nest area for two to three weeks during which time the parents continue feeding them. The nestlings gradually begin feeding themselves during this period. When conditions are favourable Blue Swallows are double brooded, certain pairs being capable of raising two sets of nestlings in a single breeding season. Adverse weather conditions as a result of mist and rain often result in Blue Swallow eggs not hatching or nestlings not fledging (Evans & Bouwman 2000). In some seasons this seriously affects breeding success. Fiscal Shrike has been recorded predating both Blue Swallow eggs and nestlings.
Threats
The major reason for the reduction in surface areas and fragmentation of these two grassland types and the concomitant endangered status of the Blue Swallow has largely been as a result of commercial forestry for the timber, pulp and paper industry (pine, eucalyptus and wattle plantations). The high altitude, high rainfall, mist-belt grassland areas that are characteristic Blue Swallow habitat are unfortunately also highly suited for the commercial cultivation of these exotic trees. In Zimbabwe the borders of Nyanga National Park are easily found as wattle and pine plantations have been planted right up to the edge of the park. Private ownership of the mineral rights to most of the Blue Swallow localities in Mpumalanga represents a current and potential future threat (Evans 1996). Increased tourism activity and development has resulted in the loss of Blue Swallow breeding pairs in the Mac Mac and Graskop Townlands area. This highlights the need for careful consideration and proper planning of tourism ventures (Evans 1997). Other reasons for the decline in and vulnerable status of the Blue Swallow and its grassland habitats are habitat destruction and fragmentation due to potato, maize and sugar cane cultivation, road construction, overgrazing and inappropriate annual burning of grasslands to improve grazing potential. The annual burning of grassland types that should be burnt every two to three year’s results in a drastic decrease in overall biodiversity. A factor resulting in a reduction in the breeding success of Blue Swallows in certain breeding areas is disturbance of the birds at the nest by the young boys herding the cattle on tribal grazing lands (Boycott pers comm).
Conservation
Due to the migratory nature of the Blue Swallow it is necessary to focus conservation action, advocacy and monitoring over its entire distribution range. Conservation activity should be aimed at preventing the status of the Blue Swallow from deteriorating further. This is achieved by working at resolving conflicts between the requirements of the Blue Swallow and the factors threatening the future existence of those requirements.
The Blue Swallow is listed on both Appendix I and II of the international Convention for the Conservation of Migratory Species of Wild Animals (CMS).
Protected Areas, Natural Heritage Sites and Important Bird Areas
Malolotja Nature Reserve (IBA SW001) in Swaziland and Impendle Nature Reserve (IBA SA077) in KwaZulu-Natal are the only formally protected areas holding breeding Blue Swallows; with totals of eight pairs each. Another 22 breeding pairs of Blue Swallows are protected in six Natural Heritage Sites; three in Mpumalanga and three in KwaZulu-Natal. The KwaZulu-Natal Mistbelt Grasslands (IBA SA078), a series of disjointed grassland patches in a farmland mosaic, hold 38-55 Blue Swallow breeding pairs (Johnson et al. 1998). The nine breeding pairs in the Blue Swallow Natural Heritage Site (IBA SA014) in Kaapsehoop represents the highest breeding density for South Africa (1 pr/52 ha) (Allan et al. 1988). The Graskop Grasslands (IBA SA011) and Misty Mountain Natural Heritage Site (IBA SA013) hold 14 and 2 breeding pairs of Blue Swallows respectively. Blyde River Canyon (IBA SA010) contains a single breeding pair with the possibility of a further pair.
End
January 24th, 2007
news.cornell.edu
When tree swallows start earlier, they often lay more eggs, say the biologists, referring to data collected by thousands of volunteer citizen-scientists who have watched the birds’ nest boxes for 40 years.
“We don’t know whether earlier lay dates and larger clutch sizes will be good in the long term for populations of tree swallows,” said David W. Winkler, a Cornell professor of ecology and evolutionary biology. “And tree swallows are just one of the many organisms that potentially can be affected by climate change.”
After an exhaustive, three-year statistical analysis of bird and weather data, Winkler, Peter O. Dunn of the University of Wisconsin-Milwaukee and Charles E. McCulloch, a biostatistician at the University of California-San Francisco, report the effects of climate change on swallows in the PNAS Online Early Edition, week of Sept. 23, 2002. Their article is titled “Predicting the effects of climate change on avian life history traits.”
Tree swallows (Tachycineta bicolor) are astute weather monitors, Winkler explains, because of three characteristics:
They are aerial insectivores, hunting the insects they crave “on the wing.” (An adult tree swallow can capture as many as 50 insects before returning to the nest and feeding its young.)
Tree swallows are “income breeders” that rely, more than many other species, on their daily foraging intake — both before and during the spring breeding season. (Tree swallows begin breeding once their source of insect income looks large enough, but the future of their growing family is at the mercy of sometimes-fickle weather.)
Insects the swallows need do not fly during cool weather, and swallows will not forage on the ground. (A sudden cold snap and a local shortage of insects can kill 5- to 8-day-old nestlings before their developing bodies learn to thermoregulate and grow insulating feathers. When adult tree swallows are forced by cool weather to travel greater distances in search of insects, they may be forced to abandon their chicks.)
Professional ornithologists rely on trained amateurs in volunteer programs, such as the Cornell Lab of Ornithology’s Nest Record Card Program, to report on birds throughout a wide geographic area. In 1999, after studying 21,000 nest records from Cornell’s database and similar programs in Canada, Dunn and Winkler reported that the lay date of tree swallows shifted an average of nine days earlier between 1959 and 1991.
Since that report, which was among the first to link animal-behavior changes to global warming, Winkler and Dunn have worked with McCulloch and extended the analysis to another key life-history trait — the number of eggs birds lay each year.
“One of the strongest patterns in this data set showed birds that begin earlier in a given season tend to lay larger clutches of eggs,” Winkler recalled. “We wanted to see if earlier average lay dates over the past 30 years have led to larger clutches. However, it is interesting to find that, despite the change in lay dates, there has been no significant increase in clutch size across the years.”
To say more with any certainty will require a much better understanding of how birds respond to climate change — and more detailed, hands-on research than even the most dedicated legions of volunteers can conduct. Nevertheless, the PNAS authors believe that their statistical analysis of tree swallows’ response can be a template for studies by other researchers of how climate change might affect various plant and animal species.
“Tree swallows are doing a fine job of observing seasonal climate conditions and responding in a way that’s easy for us to measure,” Winkler noted. “Clearly, they’re laying eggs earlier on average. Our job as biologists is to learn more about the birds and their food organisms in order to understand the effects of this and other responses to climate change.”
The study was sponsored, in part, by the National Science Foundation and Cornell.
January 23rd, 2007
braw.org
Gary Gaard, BRAW Board of Directors
I’ve had a bluebird trail at Deer Valley Golf Course for several years. I monitor ten flyGuard houses on the course. Cavity nesters at this golf course have been victim of the black fly.*
When I first placed bluebird houses on this golf course, 50% of nests were bluebirds and 50% were tree swallows.** If a location had a bluebird nest, I would leave the house at that location. Some locations have had double bluebird nests for multiple years. If a nest box had a tree swallow nest, I would move the house to a location that I hoped would be more attractive to the bluebird.
The summer of 2004 there were zero nesting attempts by tree swallows. Ten nest boxes (100%) did have nesting attempts by bluebirds.
I think there are two key factors to the bluebird nesting success at Deer Valley. All nest box placements have nearby shrubs/trees where the bluebird perches and watches the nest box. The bluebird is not the passive bird they are often portrayed; rather they will aggressively defend their nest by attacking other birds that approach the nest box. Some bluebird pairs even defend the nest by divebombing encroaching humans. Second, all houses are now in areas where hillsides have remnant prairie plants (DNR prairie plant experts monitor prairie plant populations several times during the growing season). The bluebirds are often observed hunting for insects in this remnant prairie, and I suspect abundant food supply is key to nesting success.
* Gaard, Gary. When the Buffalo Gnat Hordes Hit Mt. Horeb, Wisconsin Bluebird, fall 2004, Vol. 19 page 11.
** Gaard, Gary. Eliminating Black Fly Feeding on Nestling Bluebirds, Wisconsin Bluebird, summer 2003, Vol. 18 page 1.
January 22nd, 2007
Swallow-tail kites found nesting in the White River National Wildlife Refuge
thenewsstar.com
Arkansas Game and Fish Commission
sports@thenewsstar.com
A multi-year research project offers hope that an extremely rare bird may find a new home territory in Arkansas.
And this is not the heralded ivory-billed woodpecker. It’s the swallow-tail kite. That’s a raptor, a bird of prey in the category of hawks and falcons.
A pair of swallow-tail kites have been nesting in the White River National Wildlife Refuge in southeast Arkansas for the past few years, and this season were joined by a third one, who did not receive an enthusiastic welcome from the first two, according to researcher Sabine Schaefer.
These kites are somewhat similar in appearance to the Mississippi kite, a bird seen fairly frequently soaring in various areas of Arkansas but usually in the vicinity of major waterways. The swallow-tail has similar gray and white coloring but is larger and has the deeply-notched tail that provides its name.
Schaefer, a native of Germany, is working on her doctorate at Arkansas State University with the swallow-tail kite research. It’s a project involving the Arkansas Game and Fish Commission, with Dr. Jim Bednarz of ASU directing it.
For nearly 60 years, no swallow-tail kites were seen in Arkansas. Reports surfaced in 1998, then a search for a nest was launched in 2001 in the lower White River country, with biologist Karen Rowe of AGFC directing it. Amy St. Pierre, an ASU, found a nest of the bird in 2002 in the refuge, the first known in Arkansas in a hundred years. Troy Bater took over the research in 2004 and 2005 and found two baby swallow-tail kites that were dead , apparent victims of predator birds.
Schaefer came to Arkansas and began her work on the kites in January. The territory where the birds nest is remote, hard to traverse, but she had something of a background. She did her master’s degree work on a falcon in Mongolia.
Schaefer said, “There is so very little material available on the swallow-tail kites. We know that they nest in super-emergent trees.” That means large trees that stand above others in a forest. The nearest populations of swallow-tail kites are in Louisiana, roughly 200 miles south of the White River refuge.
Other concentrations of swallow-tail kites are in Florida, with the birds occasionally appearing in Georgia and South Carolina. Once their range was much grated, all the way to Minnesota, Bednarz said.
It’s difficult enough to find the kites’ nest, and they don’t necessarily use the same one more than one year, Schaefer said. But the nests are extremely high in very tall trees. Getting to the nests to check on eggs or chicks means climbing the trees with rappelling gear.
Again, in 2006, a predator struck the swallow-tail kite nest. Eggs were apparently eaten by a snake. Schaefer and her helper, J.P. Fairhead, installed snake guards of metal flashing cover with grease. But, Bednarz said, a snake’s trail was found going down the tree through the grease. There was no upward trail, meaning the snake was probably already in the tree when the guard was put in place, he said.
Schaefer’s work includes research on Mississippi kites in the area. She and her helper have been able to catch a few with fine-meshed nets and have installed transmitters to help record movements of these relatives of the swallow-tails.
January 19th, 2007
sacto-ucc.org
by Bruce Swinehart
No story of Spring would be complete without mention of the return of the swallows. This romanticized event is familiar to almost everyone. The swallow most often referred to is the cliff swallow, Petrochelidon pyrrhonota.
This sparrow-sized bird has the characteristically pointed wings of the swallow but is the only swallow with a square tail. The creamy-white forehead, blackish back and light brown rump spot make identification positive. The gourd-shaped mud nests are built in colonies under eaves, bridges, etc. Where these places are not available to them, they nest on rough cliffs or almost any other place they can attach their nests to. The availability of mud is an important factor.
The fact that the nests are closed on top gives them greater versatility in nesting than the barn swallow whose nest is an open cup.
Food of this fascinating summer visitor is evidently 100 percent insects. The quantity consumed by a breeding colony is tremendous. Nestlings are fed almost their own weight every day while adults will eat nearly half their weight. Insects are generally caught while on the wing. The beneficial aspect of this species should not be underestimated, and they should be protected at all costs. Large-scale insect spraying can have a disastrous effect on them. They are, of course , protected by state and federal law. The nests also come under legal protection as soon as an egg is laid in them.
The cliff swallows start arriving in central California in February. The peak of the migration is in early May. We find them along our creeks where there are nesting places like culverts, bridges and buildings with eaves. I have not noticed as many birds this year as I have in the past.
The birds spend their spring and summer in nest building, incubation, and preparing the young birds for the long migration to the remote parts of Brazil. The young must be ready for the long migration so the birds are on a narrow time frame. They all leave the area by the end of September.
At Mission San Juan Capistrano, legend has it that they always arrive on March 19th, St Joseph’s Day. There are several different legends as to why the birds come on this particular day. Birds that arrive early are either ignored or called “scouts.” Natives, however, were hard pressed to define the purpose of the scouts since they certainly did not fly back to South America to warn the other birds. According to the legend, they leave Capistrano on October 23rd, San Juan’s Day. This migration was made famous by the song “When the Swallows Come Back to Capistrano.” The swallows there are no different than the ones I used to band under the culverts of Highway 50. No one has immortalized them, however, by a song titled “When the Swallows Come Back to the Culverts of Highway 50.” Too bad!
We found after years of banding that the birds do come back to nest in large numbers in the place they were hatched. Many even return to the same area on the walls of the culvert or bridge. These are fascinating little birds, and I am pleased our creek preservation policies encourage them.
January 18th, 2007
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