Lesser goldfinches were once restricted to the south-western portions of the United States – they are common in California and Texas. The birds are present in areas of Arizona, Colorado and New Mexico and range into Central America as well. Now, the warming climate is pushing them north in significant numbers.
A new study in the journal Ornithology has found that lesser goldfinch populations have grown in states where the species was previously uncommon.
Why lesser goldfinches are moving north
According to observations from FeederWatch and eBird, coordinated by the Cornell Lab of Ornithology, numbers of lesser goldfinches have increased substantially in north-western states – growing as much as 110 per cent in Washington and 66.3 per cent in Idaho between 2012 and 2022. Populations are booming in Oregon too.
“I was seeing groups of 30 or 40 at a time and I assumed that was normal,” says lead author Mason Maron (a graduate in wildlife ecology and conservation sciences) of his early observations in Washington. Maron learned from local birders that this was a recent development – even a decade earlier, these finches were unheard of in the state.
The birds appear to be following rivers northwards, cued by warming temperatures and increased rainfall. These corridors offer an abundance of food from weedy plants that thrive along the edges of the waterways. Urban development also appears to be encouraging colonisation of these new habitats.
While birdfeeders put out by humans may tempt some of the birds, they are not enough for them to stay. The goldfinches have actually found sufficient natural food sources to establish substantial resident populations.
“Our results are suggestive of this species being able to pretty rapidly colonise new environments,” says co-author Jordan Boersma, a research associate at the Cornell Lab of Ornithology.
The Cornell Lab of Ornithology has discovered that lesser goldfinches are now less common in their native ranges, indicating that conditions there may be less favourable than the northern climes to which they are flocking. The finding is disturbing but also indicates the resilience and adaptability of migratory species in the face of radical climatic shifts.
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