Drought causes birds to nest later, reducing nesting success

A recent study suggests drought conditions are delaying nesting by two weeks or more for some Sonoran Desert bird species, such as Black-tailed Gnatcatchers and Verdins.

Despite recent rainfall, drought conditions persist in much of the southwestern U.S. Drought negatively impacts, many wildlife species, making it harder to maintain their numbers, even when adapted to a dry environment.

Newly published research from Point Blue Conservation Science (Point Blue) and the U.S. Geological Survey (USGS) finds that increased drought frequency in southwestern North America results in increased instances of delayed nesting. This delay can push the start of nesting back by several weeks in severe drought. This, in turn, makes it harder for many Sonoran Desert bird species to successfully produce young that year, as they are more vulnerable to nest predators and parasites.

"To understand how late the delay is, it would be like if the robins nesting in your yard, who typically begin nesting in late April, did not begin to nest until nearly Memorial Day," says Chris McCreedy, Point Blue ecologist and the study's lead author.

The study's authors found that after winters of low rainfall, all 13 Sonoran Desert bird species that were monitored experienced delayed nesting. As climate models are nearly unanimous in their predictions for increased drought frequency in southwestern North America, this finding raises concern for the long term health of desert bird populations.

The findings also show that some Sonoran Desert species sometimes forego breeding entirely during extreme drought.

"Other studies correlate with our findings, perhaps indicating a more widespread delayed nesting of birds in arid ecosystems," says McCreedy. "These responses are predicted to become more frequent and extreme, due to climate change, causing us to question how desert birds will persist in the long-term."

This study highlights drought as a key threat to bird in arid landscapes. In the recent 2014 National State of the Birds Report, birds in arid landscapes were found to show the steepest declines, nationwide.