As regular CFZ-watchers will know, for some time Corinna has been doing a column for Animals & Men and a regular segment on On The Track... particularly about out-of-place birds and rare vagrants. There seem to be more and more bird stories from all over the world hitting the news these days so, to make room for them all - and to give them all equal and worthy coverage - she has set up this new blog to cover all things feathery and Fortean.

Friday, 2 December 2016

Climate affecting avian breeding, study shows

Date: November 22, 2016
Source: Boise State University

Milder winters have led to earlier growing seasons and noticeable effects on the breeding habits of some predatory birds, according to research by Boise State biologists Shawn Smith and Julie Heath, in collaboration with Karen Steenhof, and The Peregrine Fund's Christopher McClure. Their work was recently published in the Journal of Animal Ecology under the title "Earlier nesting by generalist predatory bird is associated with human responses to climate change."

Smith and his co-authors studied the American kestrel (Falco sparverius), also known as a sparrow hawk, because the bird is widespread and responsive to environmental change. Their question was whether the warming climate had led to changes in prey abundance and a corresponding change in when the birds nested.

Their study looked at kestrels that nested in both non-irrigated shrub and grasslands and those that nested in irrigated crops and pastures. Using data from remote satellites to determine the greenness of different types of vegetation they were able to determine the start of the growing season for different areas. That is important because peaks in vegetation greenness correspond with peaks in kestrel prey, like small mammals and insects. They then looked at how that matched up with kestrel nesting patterns.

Results show that over the period of 1992-2015, the greenness on irrigated lands occurred earlier because of earlier planting of crops following relatively warm winters, but there has not been a change in green-up on non-irrigated lands. Kestrels seemed to "track" the changes in irrigated lands and were nesting 15 days earlier than they used to nest. Although this might not seem like much of a shift, the earliest nesting kestrels can now raise two broods per year instead of one.

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