Archive for August 30th, 2006
findarticles.com
We studied the frequency of intraspecific brood parasitism and physical transfer of eggs between nests in colonially nesting Cave Swallows (Petrochelidon fulva) and Cliff Swallows (P. pyrrhonota) in south Texas in 2001. Although the eggs of the two species look similar, frequency of brood parasitism in each species was unaffected by presence of the other species, which suggests that the parasitism we observed was largely by conspecifics. We detected brood parasitism in 4.6-5.0% of Cave Swallow nests and in 10.7-11.9% of Cliff Swallow nests. Brood parasitism was not significantly related to colony size in either species, to eventual success of the host nest, or to overall colony nesting success (a measure of environmental risk). We detected evidence of physical transfer of eggs in 0.7-2.0% of nests of these species. Cliff Swallows parasitized nests more often than Cave Swallows, but the frequencies of brood parasitism and egg transfer in the two species in south Texas appeared broadly comparable to those reported for Cliff Swallows in Nebraska, despite geographic differences in habitat, seasonality, breeding phenology, and levels of sociality between the populations. Received 28 January 2003, accepted 12 May 2004.
RESUMEN. - Estudiamos la frecuencia de parasitismo de nidada intraespecifico y de transferencia fisica de huevos en las golondrinas Petrochelidon fulva y P. pyrrhonota en el sur de Texas en 2001. A pesar de que los huevos de ambas especies son similares, la frecuencia de parasitismo en cada especie no se vio afectada por la presencia de la otra especie, lo que sugiere que en gran medida el parasitismo observado fue ocasionado por individuos coespecificos. Detectamos parasitismo de nidada en un 4.6-5.0% de los nidos de P. fulva y en un 10.7-11.9% de los nidos de P. pyrrhonota. El parasitismo de nidada no se correlaciono con el tamaño de la colonia, con el éxito eventual del nido hospedero, ni con el éxito de nidificatión general de la colonia (una medida de riesgo ambiental) en ninguna de las dos especies. P. pyrrhonota parasitó nidos con mayor frecuencia que P. fulva, pero la frecuencia de parasitismo de nidada y de transferencia de huevos en las dos especies en el sur de Texas parecen ser comparables con las frecuencias reportadas para P. pyrrhonota en Nebraska, a pesar de las diferencias geográficas en el hábitat, en la estacionalidad, en la fenologÃa de nidification y en los niveles de estructura social entre las poblaciones.AN ALTERNATIVE REPRODUCTIVE tactic in some animals is to lay eggs in nests of conspecifics and parasitize the parental effort of the hosts. Brood parasitism among conspecifics is now known for scores of bird species and some insects (Yom-Tov 1980, Andersson 1984, Rohwer and Freeman 1989, Rothstein and Robinson 1998) and, across taxa, appears to be associated especially with high fecundity (Arnold and Owens 2002). However, ecological conditions favoring parasitic laying have been investigated for only a few species, such as swallows (Brown 1984, M011er 1987, Brown and Brown 1989), bee-eaters (Emlen and Wrege 1986), coots and moorhens (Gibbons 1986, Lyon 1993, McRae 1998), starlings (Evans 1988, Romagnano et al. 1990), weavers (Jackson 1993, 1998), and waterfowl (Andersson and Eriksson 1982, Semel et al. 1988, Lank et al. 1989, Sorenson 1998, Andersson and Ahlund 2000). From those studies, it is clear that the frequency of parasitic laying varies among individuals both within and between populations of the same species.
One potential ecological determinant of conspecific brood parasitism is population density. When suitable hosts occur in high density and close proximity, such as in breeding colonies, parasitism may be a viable alternative reproductive strategy (Eadie and Fryxell 1992). Various workers have shown that in some species, conspecific brood parasitism increases with colony size or is more prevalent in larger colonies (Brown 1984, Møller 1987, Brown and Brown 1996, Lyon and Everding 1996, Hill et al. 1997), though in other species, colony size or coloniality per se has no effect (Hoogland and Sherman 1976, Lank et al. 1989, Rohwer and Freeman 1989, Davis 1998).
Colonial Cliff Swallows (Petrochdidon pyrrhonotn) show a relatively high incidence of conspecific brood parasitism (Brown and Brown 1989, 1996). In that species, brood parasitism increases with colony size and appears to be a successful reproductive strategy of high-quality individuals (Brown and Brown 1998) that involves accurate assessment of the best host nests to parasitize (Brown and Brown 1991). However, some Cliff Swallow populations have been reported to have a much lower incidence of brood parasitism (Smyth et al. 1993). Better understanding of the ecological conditions that do or do not promote brood parasitism requires comparative data, collected in similar ways, on other populations and closely related species.
The present study examines patterns of brood parasitism in a congener of the Cliff Swallow, the Cave Swallow (P. fulva), and also reports information on brood parasitism in Cliff Swallows from an area (south Texas) where that species has been little studied. We provide the first known reports of brood parasitism (including physical transfer of eggs between nests) in Cave Swallows, and we investigate how brood parasitism in both Petrochdidon swallows varies with colony size.
August 30th, 2006
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Swallows keep eggs in several baskets
Call it nature’s version of a baby left on a doorstep. Biologists have discovered that adult cliff-dwelling swallows sometimes carry one of their own eggs into the nest of an unwitting neighboring swallow, and then fly away minus the egg — a sneaky maneuver called reproductive parasitism that may increase the chance of the egg’s survival.
Birdwatchers have long known about another form of reproductive parasitism whereby birds lay their eggs in the temporarily vacant nest of another bird. Some, like various species of swallows, starlings and ducks, keep the eggs within their own species, while cuckoos are known for filling the nests of birds of another feather. But this is the first time scientists have witnessed the transfer of already-laid eggs, report Yale University biologists Charles R. Brown and Mary Bomberger Brown in the Jan. 7 NATURE.
The researchers observed this transfer while studying a community of swallows in Nebraska. They monitored the birds both by sight and by recording the movements of marked eggs between nests. Transferred eggs showed up in 6 percent of the nests. But they add that their estimate of transfer frequency is “undoubtedly an underestimate.”n one instance, a swallow transferred its egg into a nearby nest under the very beak of the nest’s occupant. “A fight ensued when the intruder entered with the egg. The intruder was evicted from the nest within 10 seconds, but the egg remained in the nest,” according to the researchers. Previous studies have shown that swallows cannot recognize eggs as foreign.
The biological significance of this practice is still unknown. But the researchers suggest it is related to survival. In the general swallow community, roughly a quarter of all eggs fail to hatch. However, only 10 percent of transferred eggs failed, leading the biologists to theorize that when a swallow transfers an egg, it chooses superior incubators as the surrogate parents.
The transfer behavior may have developed in the ancestral swallow nesting grounds of cliffs and canyons, which are the site of frequent rockfalls, say the investigators. Individual swallows may protect against losing an entire clutch to a rockfall by spreading the eggs around.
But in a comment on the report, Cambridge (England) University zoologist N.B. Davies suggests that reproductive parasitism may be more a matter of avian economics. “A more likely explanation perhaps,” he says, “is that parasites increase their lifetime reproductive success by reducing the costs of parental care.”
August 30th, 2006
Daily Vidette - Aug 22 8:48 PM
Once again, the University Program Board will be sponsoring the Weekly Wednesday Lunchtime Special in The Bird’s Nest located in the Bone Student Center.
The program will feature many local artists as well as nationally touring singers and songwriters. It will take place every Wednesday from 11 AM to 1 PM and is free to the public.
Emily Villhauer, UPB advisor and specialist for programming with the dean of students office, said she is very excited about the upcoming entertainment.
“It’s a minimal program but it gives a great opportunity to showcase students and local performers,” she said.
ISU students and other local performers are invited to show off their talents at the events also.
“If students are interested in performing either for an hour or the whole two hours, they can fill out an application that’s available on the UPB website or they can stop in the UPB office and fill out an application and drop off a demo,” Villhauer said.
The first few weeks include nationally touring singer and songwriter Shevy Smith on Aug. 22 and ISU student Jason Fingh with special guest Dave Degoyeer on Aug. 30.
Smith has performed at ISU in the past and has always been a favorite among students.
“She did great,” Redbird Entertainment Committee Chair Person Kevin Parkinson said.
“She’s been here twice before. The students that attend her events really seem to enjoy her music,” Villhauer said.
The Lunchtime Special is returning for its second semester at ISU. This year the program will focus more on local performers.
“Last year we did more national artists, we did about half national and half local, and this year the students decided they wanted to really give an opportunity for local students or musicians to showcase their talents,” Villhauer said.
“Students really like the national acts so we kept two,” Parkinson said. In addition to Smith, the second national act will be Michael Warren who will be performing in December.
Fingh, who will be performing on Aug. 30, is very excited about his second appearance in The Bird’s Nest. The sophomore mathematics major played during the Lunchtime Special last spring.
He will be performing with Degoyeer who also plays guitar and sings.
“I write a lot of contemporary Christian music but I also do a lot of covers, so I’ll be doing both,” Fingh said.
The program has been very successful and seems to be a perfect fit for ISU.
“Once the new area opened upstairs with the Burger King and Pizza Hut, they put in this new lounge furniture and they built a little stage up there. It was kind of just a perfect place to do something weekly. We’ve heard of other programs at other schools that have gone really well doing a weekly showcase of student performers,” Villhauer said.
“The room is now wired for sound as well, so it’s got permanent speakers in there. It’s an easy place to move the necessary sound equipment like the mixing board. We can move that in, do this and then be out within three hours.”
Burger King and Pizza Hut are both open with normal prices throughout the events but spectators are not required to buy any food in order to watch the performers. Outside food is also welcome in the lounge.
UPB has been taking applications over the summer and will continue taking them throughout the year. They have plenty of open dates and they urge students to sign up. Their office is located on the bottom level of the Bone Student Center and their website is programboard.ilstu.edu.
August 30th, 2006