Birds will raise fewer chicks in the coming decades because of climate change, warns new research.
An earlier spring makes it harder for them to know when it is time to breed, the new report reveals.
Just as autumn leaf fall is being delayed by warmer weather, flowers are appearing earlier on trees and shrubs.
There are knock-on effects for birds, insects and whole ecosystems.
Global warming is causing spring to arrive early and autumn to come late in many places. Not all plants and animals are adapting at the same rate.
Conservation strategies should address birds’ responses to climate-driven shifts, says the US team.
Determining if the earlier springs will pose problems for migratory birds has been a major goal of biologists for decades.
When it comes to raising their young, timing matters for birds. If they breed too early or too late, harsh weather could harm their eggs or newborns.
The same applies to food. If birds are looking for grubs before or after their natural availability, they might not have the resources to keep their young alive.
Satellite imaging determined when vegetation emerged around each location. The study found each species had an optimal time to breed.
The number of young produced decreased when spring arrived very early, or when breeding occurred early or late relative to when plants emerged.
Most were adversely affected by variations in the start of spring. Several species countered the trend, demonstrating improved breeding productivity when spring began earlier.
They included the northern cardinal, Bewick’s wren and wrentit. They are non-migratory species that can respond more quickly to the emergence of spring plants that signal the start of the breeding season.
By breeding earlier and without the time constraints imposed by migration, non-migratory species may also be able to reproduce more than once per season.
But those species were the exceptions to the rule. Even most non-migratory species couldn’t keep up with earlier spring arrivals. Overall, for every four days earlier that leaves appeared on trees, species bred only about a day earlier.
For migratory species breeding is likely to get shorter as spring-like conditions begin earlier.
Birds need time to establish territories and prepare physiologically for egg-laying and rearing their young.
The change could cause even greater disturbances to reproduction.
Produced in association with SWNS Talker
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