Literature Review: Ornithology

by Carl Strang

Birds are the focus of this week’s literature feature.

The superb fairy-wrens of Australia have revealed yet another amazing wrinkle in their biology.

The superb fairy-wrens of Australia have revealed yet another amazing wrinkle in their biology.

Diane Colombelli-Négrel, Mark E. Hauber, Jeremy Robertson, Frank J. Sulloway, Herbert Hoi, Matteo Griggio, Sonia Kleindorfer. Embryonic Learning of Vocal Passwords in Superb Fairy-Wrens Reveals Intruder Cuckoo Nestlings. Current Biology, 2012; DOI: 10.1016/j.cub.2012.09.025

As described in a ScienceDaily article. They noticed that female superb fairy-wrens sing to their eggs, and they later demonstrated experimentally that the mothers were teaching their future nestlings a particular note, described by the authors as a password, that the nestlings would need to include in their begging calls to be fed. This note varies from nest to nest, and if the parents do not hear it they abandon. This is a novel way of dealing with nest parasites, in this case cuckoos, whose eggs and nestlings do not have the programming to learn and repeat the password.

Katzner, Todd, et al. 2012. Status, biology, and conservation priorities for North America’s eastern golden eagle (Aquila chrysaetos) population. Auk 129:168-176.

The eastern population estimate is 1000-2500 (east of the Mississippi River; western population 21,000-35,000). The species generally appears to be declining, though the eastern population has increased since the ban on DDT. Lead poisoning and incidental damage by leg-hold traps set for mammals are the biggest threats to eastern eagles. They are most abundant in Quebec, fewer in Ontario and Labrador as breeders. There has been no nesting in the eastern U.S. since the late 1990’s, the last ones in Maine and New York state. In Canada, nest sites are away from forested areas, mainly “at the interface of tundra, boreal forest, and wet meadows.” An estimated 15-25% migrate through the Great Lakes region. Wisconsin and Iowa host at least 70 birds in winter; the wintering status in Illinois is given as “unknown.”

The next study supports the idea that birds are more diverse in the tropical forests because of that biome’s greater age.

The next study supports the idea that birds are more diverse in the tropical forests because of that biome’s greater age.

W. Jetz, Thomas, G. H., Joy, J.B., Hartmann, K. & A.O. Mooers. The global diversity of birds in space and time. Nature, October 31, 2012.

As described in a ScienceDaily article. They did a combined fossil and DNA study of 10,000 bird species, and found unusual evolutionary diversification has been happening over the past 50 million years. Furthermore, the rate of new species appearance has not leveled off, but rather continued or even increased, in contrast to the usual pattern in which a foundational species diversifies but then a plateau is reached when available niches are filled. They attribute this difference to birds’ mobility, the opening of new habitats, and certain adaptable avian traits. Furthermore, there is no difference between speciation rates in the tropics and more polar regions, supporting a longer continuous history of tropical environments as being responsible for greater tropical diversity of birds (species accumulating, but extinction less rapid).

Stanley CQ, MacPherson M, Fraser KC, McKinnon EA, Stutchbury BJM (2012) Repeat Tracking of Individual Songbirds Reveals Consistent Migration Timing but Flexibility in Route. PLoS ONE 7(7): e40688. doi:10.1371/journal.pone.0040688

They followed individual wood thrushes over several migrations, and found that individuals showed little variation in spring migration departure date, and arrival date on territory, but much more flexibility in migration route and in fall departure date.

Brommer JE, Lehikoinen A, Valkama J (2012) The Breeding Ranges of Central European and Arctic Bird Species Move Poleward. PLoS ONE 7(9): e43648. doi:10.1371/journal.pone.0043648

They compared breeding bird atlases conducted in Finland, finding that there have been shifts northward in the centers of ranges for both northern and central European species. The shifts are happening slowly enough that surveys need to be taken decades apart. Northward advance of the northern edges of ranges is happening more quickly than extinctions at southern edges. The latter consideration is needed if range shifts are to be attributed to global climate change.

Lessons from Travels: Platypus Pool

by Carl Strang

When I traveled to Australia in 2000, the animal I most wanted to see was the platypus. Arguably the strangest mammal in the world, that egg-laying monotreme reportedly is difficult to observe. When I reached Mount Field National Park in Tasmania, I heard that platypuses are seen regularly in that area. After a day’s exploration of that beautiful park I still hadn’t found one, though. I mentioned my interest to the couple that ran the National Park Hotel, where I was staying, and they made a phone call.

The National Park Hotel. “Cascade” is a popular local beer.

The National Park Hotel. “Cascade” is a popular local beer.

National Park Hotel, interior hallway. The word “quaint” comes to mind, meaning “pleasingly old fashioned.”

National Park Hotel, interior hallway. The word “quaint” comes to mind, meaning “pleasingly old fashioned.”

My hosts arranged for me to go into a local golf course which had not yet opened for the season. They said they liked to go there in the evening and sit above a pool in the river, with the national park boundary on the opposite side. When I got there I found out why. I am now several months into my 62nd year, and I have never in all that time found a place where I felt more at peace than I did that morning at Platypus Pool. I sat at the top of the bank overlooking the river, which was 20 yards wide and had a few fallen logs in it. Birds sang their spring songs, eucalypts on the opposite side occasionally shed bark strips, and a brilliant male superb fairy wren came through just beneath me, his foraging behavior sometimes chickadee-like, sometimes wren-like.

From my trip diary: “I sat on a rock, enjoying the peace of the place and surveying the pool below, and within 2 minutes a platypus appeared. It worked its way along the far edge of the pool, giving me a good look. I even snapped a quick picture. A second platypus soon appeared. They nosed their way along the far bank, swimming among the fallen logs and sticks, both swimming along the surface and diving down. They were easy to spot when present, because of the ripples they formed when breaking the water’s surface. One crossed the river at the upstream end of the pool, swimming across the surface to do so. A couple of times a platypus rolled over near the surface of the water, reminding me of an otter.”

The best I could do with my old film camera. You can make out the general shape of the platypus.

The best I could do with my old film camera. You can make out the general shape of the platypus.

My lasting impression, however, was that the platypus was most reminiscent of a muskrat, from its size, the way it dove for food, used the current, floated on the surface. Like muskrats in streams they use bank den tunnels, and include plenty of mollusks in their diet, though they don’t eat plants nearly so much, if at all. So, I saw my platypuses, and had a morning that will remain one of the highlights of my life.

Literature Review: Using Your Enemy

by Carl Strang

Some observations are just plain cool. A ScienceDaily article reported on a study in Australia that may or may not be relevant to our birds, but certainly should have me listening for inter-species patterns in their singing from now on. Here’s the reference: E. I. Greig, S. Pruett-Jones. 2010. Danger may enhance communication: predator calls alert females to male displays. Behavioral Ecology 21: 1360. The abstract can be accessed here: 10.1093/beheco/arq155.

Superb fairy-wren, a close relative of the study species. Their overall behavior reminded me of a chickadee’s, with the addition of wren-like tail cocking.

Grieg and Pruett-Jones conducted experiments showing that splendid fairy-wren males attach a particular courtship song to that of a predator (butcherbird), so that it resembles a duet between the species.

The pied butcherbird is a predator comparable to our shrikes. It has a beautiful, complex song, with frequent pauses where a fairy-wren easily could insert its own phrases.

The study showed that this made it more likely that a female fairy-wren would notice the song, as the predator’s song raised her alertness.

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