The conference continues. This is my second to the last day at the joint conference of the Cooper Ornithological Society, the American Ornithologists' Union, and the Society of Canadian Ornithologists in San Diego. While all of my classmates were pouring their blood into the Mammalogy exam, which I am missing, I donated blood for science! UCLA has a multi-year study into avian influenza. They are sampling as many individuals with bird handling experience as possible for avian influenza antibodies. I decided to pitch in some of mine. There was a pretty good number of individuals donating blood so it should be an effective study.
The plenary talk this morning was the actual person scheduled to give the talk! The focus of the talk is on cavity nesting webs. This integrative presentation included studies from around the world of forest make up, primary cavity excavators such as the larger woodpeckers, secondary excavators such as nuthatches, and then cavity users such as bluebirds. Cavity nesting birds make up 15-50% of forest species within a given ecosystem and range from as small as 6 grams (Lucy's Warbler) up to 5 kilograms (Southern Ground Hornbill - another bird I recently saw in Kenya for the first time). The studies have shown that cavity availability directly effects both quantity and diversity of other species including birds and mammals. The presence of other kingdoms such as fungus also play a critical role. The talk emphasized the complex relationships required for a healthy cavity ecosystem - including the trees, the fungus, all of the birds and mammals. It was interesting to see how the webs are similar and different between locations with and without primary excavators. Some locations without cavity excavators have more natural holes available and they generally last longer than other areas. The real problem is that cavities take a long time to become available. In some places a cavity tree way have to be 100 years old before become a prime target. These trees are also the targets of industry either for logging or clearing for agriculture.
For the morning science sessions I focused on the conservation theme. The first three talks were based on the Illinois bird survey. Illinois has data from scientific surveys performed 100 years ago. They have repeated the surveys and calibrated the results with other surveys such as Audubon's Christmas Bird Count. Much has changed, some species have won, most have lost. The winners are those that are well adapted to human developments such as Canada Geese, Ring-billed Gulls, and Turkey Vultures. The losers include those that are dependent upon the historical make up of the area - grass, shrubs, marsh, and savannah. The other talks included focused studies of the Swainson's Warbler, the Tricolored Blackbirds, the American Kestrel, and the California Condor. After a little too much information on how human land use is systematically destroying species, I decided to get a little change of pace. I moved over to the brood parasitism track and picked up some interesting talks there. Brood parasitism occurs when one individual lays eggs in another's nest. The parasitized bird then takes on all of the responsibility of raising the young. This occurs between species and within species. The first discussion covered how the first egg in an American Coot's nest is used to imprint the related chicks to the adult. If the first egg hatched belongs to that parent, the siblings of that egg are most likely to be accepted by the adult. If the first egg hatched is a parasite, the adult is more likely to accept the siblings of that parasite over her own. In the next talk the focus shifted to whether or not singing at a nest increases parasitism. Many studies have shown this to be true. But in the Least Bell's Vireo, singing near the nest appears to decrease parasitism. In this species, singing near the nest increases nest attentiveness, which decreases parasitism by decreasing opportunities for the parasite. The last talk in this session covered whether the type of song of the target species attracts Bronze Cowbirds (parasite species). This study showed that the song does attract the cowbird, but at different rates between species. Oriole songs attracted more cowbirds than sparrow songs for example. This is likely due to the success of previous parasitism with that species, but it is unknown if this is learn behavior or genetic.
My afternoon agenda focused on molt, migration, and stopover biology and then on population ecology. The molt studies included controlled experiments into whether interaction with a artificially induced breeding mate (via hormones) will delay molt in its pair (it didn't), and what the effect of double brooding (raising two clutches instead of one) has on annual molt in the Wood Thrush (delays molt, higher corticosterone, overlaping molt/migration, but no delay at wintering grounds). A stopover study demonstrated three different approaches to measuring weight gain at a New England migratory stopover sites (all species gained weight during autumn migration as measured by all three methods, but not in the spring - probably thinking too much about mating). One study used radio tracking of Wood Thrushes to determine if August body condition predicted arrival on the wintering grounds two months later (it does).
For the population ecology sessions there were a number of interesting presentations. The first studied carry-over effects by using stable isotope measurements to determine if winter habitat quality and location, determined by different isotopes, predicted breeding territory arrival dates. There were only limited conclusions which could be made in older female migrants, but the second year of data has not yet been analyzed. The next study continued the theme investigating carry-over effect of Wood Thrushes on reproductive output. This study also uses isotopes from both breeding and non-breeding range and geo-locators. Are there any Wood Thrushes out there without locators??? Reproductive output was measured by arrival corticosterone and 1st egg date. Findings: early departure did not equate to early arrival, early arrival did equate to early egg, days migrating equated to higher corticosterone (stress) not lower, and the higher stress delays reproduction.
Next up: survivability of a neotropical passerine - Western Slaty Antshrike. What factors influence first year survival? Low support for sex, year, or body mass. Highest support for day of year - safest is the middle of reproductive season. Now on to wolves! Thought this was a bird conference? Ok, Wolves and Ravens. This study looked at the population responses of the Common Raven to reintroduced Grey Wolves. Ravens have adapted to respond to wolf vocalizations, follow tracks, and follow wolves directly. Utilizing the wolf kill database maintained by the wolf project in Yellowstone National Park, the team found a very positive relationship between wolf kills and the number of the ravens, and thus the number of wolves and number of Ravens in a given area. They then looked across the west to see if the reintroduction of wolves has shown up in the various Breeding Bird Survey and Christmas Bird Counts. It has actually shown a decrease in Raven numbers. There are a number of possible explanations, but further study is required. The most likely is that Ravens are attracted away from the count sites and humans, back into the wilderness, but we really don't know. The study continues.
Its been another full day of great research. Wow, so many cool projects that would be great to work on. I have a number of ideas in my head for possible master projects. I need to look at the literature to see which of them might be novel. Cool stuff. One more day to go, then I head home.