It’s time once again for some Bird Science! Here are a couple of interesting research reports on birds from distant shores.
1) Having good neighbors is good for you.
Kat Bebbington et al. Kinship and familiarity mitigate costs of social conflict between Seychelles warbler neighbors. Proceedings of the National Academy of Sciences, October 2017 DOI: 10.1073/pnas.1704350114
This study looks at how the identity of your neighbors affects your physiological well being. The Seychelles Warbler lives in a predator free habitat on the Seychelles Islands in the Indian Ocean. The birds live a fairly long time and maintain territories over their lifespans. The birds in neighboring territories vary in how closely related they are to one another. They also vary in how familiar they are to one another, based on the length of time they’ve been sharing a border.
The researchers hypothesized that interactions with relatives are likely to be less stressful than with non relatives and that interactions with familiar birds are less stressful than interactions with unfamiliar birds. The former hypothesis is based on the idea of kin selection, that selection can favor cooperation with relatives due to genetic similarity through common ancestry. The latter hypothesis is based on the idea that repeated contact with the same neighbor provides information on what to expect in future encounters. Once boundaries have been established less energy may be required to defend them.
Island populations are ideal for this type of study as there is limited movement of birds in and out of the area and individuals can be followed over very long periods. The researchers were able to measure average relatedness and familiarity of neighbors for each bird and then correlate that to two measures of physiological condition: body mass (corrected for body length) and telomere length. The first is pretty straightforward, it is the weight of the bird, adjusted for its linear size. This is a commonly used measure of physical condition in animals, generally stressed, sick or starving animals are going to be lighter for a given size than healthy animals. Being overweight is not really a health issue in wild animal populations unless fed by humans. For flying birds this measure is a bit problematic as heavier than average individuals may be a bit less maneuverable and thus able to escape predators. However in this bird that is not an issue.
Telomere length is a bit more abstract. Telomeres are ‘caps’ of repetitive DNA (the same sequence of DNA bases over and over) that occur at the ends of chromosomes. A chromosome is actually a very long (double) strand of DNA. When a chromosome is copied the the two strands separate in many places and a new matching strand is built onto each of the old strands until two new double strands are built, each containing one ‘old’ strand and one new strand. A problem arises at the end of each strand because the machinery for building a new strand onto can only work in one direction. Thus a small bit at the end can’t be copied and the new strand is slightly shorter than the old one. If that lost DNA were part of a functional gene that would obviously be bad. The telomeres protect the rest of the chromosome but a bit of them gets lost each time a cell divides and new chromosomes are made. Thus telomeres shorten as individuals get older and their cells have divided more often. Telomere length has been used as a measure of physiological age and overall condition. This is controversial and viewed as simplistic by some researchers.
Above is a very thorough explanation of the basics of telomeres if you are interested. It is 13 minutes long FYI.
This study found that having familiar and/or related neighbors was correlated with good body condition and longer telomeres. So it seems that having non-stressful neighbors is pretty important.
At first I thought this was the only youtube video of this species.
But apparently not because this video provides some interesting background. Apparently this study was done on the entire world’s population of this species.
2. What Do Albatrosses Eat?
Julie C. McInnes, Rachael Alderman, Mary-Anne Lea, Ben Raymond, Bruce E. Deagle, Richard A. Phillips, Andrew Stanworth, David R. Thompson, Paulo Catry, Henri Weimerskirch, Cristián G. Suazo, Michaël Gras, Simon N. Jarman. High occurrence of jellyfish predation by black-browed and Campbell albatross identified by DNA metabarcoding. Molecular Ecology, 2017; 26 (18): 4831 DOI: 10.1111/mec.14245
Julie C. McInnes, Simon N. Jarman, Mary-Anne Lea, Ben Raymond, Bruce E. Deagle, Richard A. Phillips, Paulo Catry, Andrew Stanworth, Henri Weimerskirch, Alejandro Kusch, Michaël Gras, Yves Cherel, Dale Maschette, Rachael Alderman. DNA Metabarcoding as a Marine Conservation and Management Tool: A Circumpolar Examination of Fishery Discards in the Diet of Threatened Albatrosses. Frontiers in Marine Science, 2017; 4 DOI: 10.3389/fmars.2017.00277
These are two papers from the same group using molecular data (i.e. extracting DNA from the feces of albatrosses) to investigate the diets of albatrosses, primarily the black-browed albatross which is the most abundant of the Southern Hemisphere albatrosses. The first paper reported the somewhat surprising finding that albatrosses ate a lot of jellyfish. This is surprising because jellyfish are relatively low in nutritional value and jellyfish specialists tend to be large massive animals such as leatherback turtles and ocean sunfish. However jellyfish are often floating along at or near the ocean surface and easily accessible to albatrosses.
The second paper found that the amount of type of fish in albatross diets was correlated to fisheries practices in the region in which they fed. If there was a lot of discarding of fish by fishing ships then the discarded fish species showed up in the diet to a large extent. Anyone who has ever observed a fishing boat out at sea has noticed sea birds following. Long-lining kills large numbers of albatross and other sea birds and this research suggests that the amount of discarded fish may strongly influence the foraging behavior of albatrosses and thus the likelihood of being caught on a long line.
I couldn’t find a really relevant video. This is people feeding albatross in Half Moon Bay on the coast of Stewart Island in southern New Zealand. This is the only place I’ve albatross while standing on solid ground (although these people are in a boat).
That’s it for the science. Bird away in the comments. I may be away until 11 or so eastern time but will check in as soon as I get back home.