Little is known about songbirds that breed in alpine habitats. ECCC researchers set out to learn about how they adapt to extreme weather conditions.
A University of British Columbia (UBC) research team led by Devin R. de Zwaan, and ECCC scientists Kathy Martin and Alaine Camfield studied the factors influencing chick development in songbirds. Their article, “Variation in off-spring development is driven more by weather and maternal condition than predation risk,” was recently published in the journal Functional Ecology.
In order to understand how birds breeding at high elevations adapt to highly variable climatic conditions (subzero to 40+ degrees), the researchers focused on the horned lark, a declining songbird that breeds in the mountains of Northern British Columbia. In order to breed successfully in habitats with very short breeding seasons and extreme weather events birds need to be resilient. Understanding the strategies that alpine birds use to survive and reproduce in these high mountain habitats may help us identify ways that animals can adapt to climate change.
Results
One adaptation to highly variable environments is for birds to have flexible nesting strategies. Horned larks are excellent example of this strategy, as their chicks may leave the nest in as little as seven days, or as long as 13 days. In many species of birds, the length of the breeding period is determined by the relative risk of predation at each stage. However, this study shows that in alpine breeding birds, extreme weather and the ability of the parent birds to buffer the eggs and young predict the length of the breeding period.
“This is a unique finding since in most ecosystems predation is the main driver of incubation and nestling periods,” said Camfield.
Colder temperatures tend to increase the period of incubation and reduce chick growth rates. This forces females to trade-off between tending the nest or feeding their young, decisions that can impact both chick growth and future female survival.
“These birds are very good at dealing with storms but if the storms are cold, nests are much more likely to fail,” says Martin. “Horned Larks also can not handle long periods without some kind of sustenance and if there’s a multi-day storm, food becomes less available.”
Next Steps
This study has shown how changes in weather might affect populations of Horned Larks, but in order to conserve this declining population we also need to understand impacts over the annual cycle. De Zwaan and his team have used geo-locators to track the migration route of the larks to their wintering grounds in order to understand potential impacts in these habitats on their subsequent breeding success.
Martin says understanding their migration path each winter can provide more information about how winter conditions could influence maternal conditions for the following breeding season.
“It’s another important piece of the puzzle for the life cycle of this small but hardy songbird.”
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