Why It's OK for Birds to Be Gay

In greylag geese, nearly a fifth of all long-term couples are composed of two males. They're not alone: More than 130 bird species are known to engage in homosexual behavior at least occasionally, a fact that has puzzled scientists.

After all, in evolutionary terms same-sex mating seems to reduce the birds' chances of reproductive success. But that's not necessarily so, according to a new study. In a given species, the sex with lighter parental duties tends to mate more, period — whether with the same or the opposite sex.

Lees meer: LiveScience

Eggshells Look More Colorful Through the Eyes of Birds

Birds see a more colorful world than we do, especially when it comes to their eggs, a new study suggests.

Unlike humans, birds can see ultraviolet (UV) light, and they have four – rather than three – color receptors in their eyes, allowing them to better distinguish between hues.

Now researchers have shown that while most of the color variation in eggshells can be seen by humans and birds alike, a swath of hues that our eyes miss may play an important role in avian life. For instance, we are oblivious to the UV pigment that may help birds differentiated between their own eggs and those of another species.

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Population overlap and habitat segregation in wintering Black-tailed Godwits Limosa limosa

Auteurs: Jose A. Alves, Pedro M. Lourenco, Theunis Piersma, William J. Sutherland, Jennifer A. Gill
Bron: BIRD STUDY, Volume 57, Issue 3 August 2010, pages 381-391
Abstract:

Capsule Distinct breeding populations of migratory species may overlap both spatially and temporally, but differ in patterns of habitat use. This has important implications for population monitoring and
conservation.

Aims To quantify the extent to which two distinct breeding populations of a migratory shorebird, the Black-tailed Godwit Limosa limosa, overlap spatially, temporally and in their use of different habitats during winter.

Methods We use mid-winter counts between 1990 and 2001 to identify the most important sites in Iberia for Black-tailed Godwits. Monthly surveys of estuarine mudflats and rice-fields at one major site,
the Tejo estuary in Portugal in 2005-2007, together with detailed tracking of colour-ringed individuals, are used to explore patterns of habitat use and segregation of the Icelandic subspecies L. l. islandica and the nominate continental subspecies L. l. limosa.

Results In the period 1990-2001, over 66 000 Black-tailed Godwits were counted on average in Iberia during mid-winter (January), of which 80% occurred at just four sites: Tejo and Sado lower basins in
Portugal, and Coto Donana and Ebro Delta in Spain. Icelandic Black-tailed Godwits are present
throughout the winter and forage primarily in estuarine habitats. Continental Black-tailed Godwits are present from December to March and primarily use rice-fields.

Conclusions Iberia supports about 30% of the Icelandic population in winter and most of the continental population during spring passage. While the Icelandic population is currently increasing, the continental population is declining rapidly. Although the estuarine habitats used by Icelandic godwits are largely protected as Natura 2000 sites, the habitat segregation means that conservation actions for the
decreasing numbers of continental godwits should focus on protection of rice-fields and re-establishment of freshwater wetlands.

Warbler Fight Songs Follow Fashion While Love Songs Stick to a Few Classics

A team of researchers has found that chestnut-sided warblers possess two distinct cultural traditions in song variants that evolve independently -- one, used for territorial disputes that changes frequently, and another, used for romance that relies on a small unchanging sampling of classics. The findings suggest songbird culture is more complex than previously thought, the scientists say. The paper will be published in the journal The American Naturalist.

Lees meer: ScienceDaily