I woke this morning feeling a desperate need for some kind of good news. Something to take my mind off, um, world events? I was grateful then, to open my email and find a news release about a new study of songbirds in Pennsylvania, published in the journal Global Change Biology.
The researchers, Molly McDermott and Lucas DeGroote from the Powerdermill Nature Reserve, used five decades worth of banding data, and compared factors such as arrival times, breeding, and fledging to climate data.
It’s generally been assumed, and a number of studies have supported, the notion that a warming climate is going to be a bad thing for most species of birds, particularly migrants. A changing climate produces instability in the environment. Food resources such as insect hatches, and fruiting of plants is more variable and generally earlier in the season. Birds have traditionally timed their migrations to arrive when resources are most needed for breeding and reproduction. Climate change is a big wrench in that system, causing mis-timing between arrival and food availability which ultimately harms reproduction and survival.
But maybe that’s not always going to be the case, as this new study suggests.
McDermott and DeGroote looked at 21 species of breeding birds at their field site in Pennsylvania over the past 50 years and found that birds were adapting to the climate. Most of the species observed adjusted their arrival times, and chick fledging dates in concert with the changing availability of food.
We aren’t talking about just small shifts either. When the authors pooled data from all their study species, they found that breeding condition advanced 31 days over the course of the project. That means that some species are starting their breeding cycle a solid month earlier than they were a few decades before.
For early-breeding species on their field site, they found that young appeared an average of 22 days earlier over the course of the study. These birds are adjusting the reproductive period in large and substantial ways.
The breeding season itself also increased for some species, allowing multiple broods and for two species (Gray Catbird and Wood Thrush), dramatically increased productivity.
Perhaps the most hopeful finding in this study is that these adaptations occurred regardless of migratory strategy. Long-distance migrants have generally been considered less adaptable to a changing environment than their shorter-distance or resident counterparts. After all, birds wintering in the tropics won’t have access to the cues about food availability that more northerly species will. McDermott and DeGroote hypothesize that long-distance migrants will make their yearly movements more quickly to arrive at the breeding grounds, and also will engage in breeding a shorter time after their arrival. However it happens, both short and long-distance migrants appear able to adapt to a changing climate in a way that most researchers did not think them capable.
This is all very cool work, and I’m curious to see if other studies will back up the findings. Here in Fairbanks, the Creamer’s Field Migration Station, started by the Alaska Bird Observatory and now operated by the Alaska Songbird Institute, has been capturing and banding birds for over 30 years. I’d be very interested to see if data here in Alaska, at the northern extent of range for some of these same species, will show similar changes.
Long-term monitoring of wildlife is a tricky thing to do, it costs money, and doesn’t show immediate results. In fact, important discoveries like these, may not be available for decades. But this is great evidence for why such projects warrant the effort.
For me, it was nice to have a bit of good news today. Birds are tough little things, far more adaptable and resilient then perhaps we give them credit for. They are finding ways to succeed under extreme pressures.
Perhaps there is a lesson in that for us all.
