The impacts of climate change on spring migration

If you followed the banding lab’s efforts this spring season, one thing should have been clear: we caught a lot of birds.

 

What constitutes “a lot,” you ask? Let’s break it down:

 

 


We operate 50 mist nets in the spring (April 15 – June 15) and fall (August 15 – November 15) from dawn until dusk, Monday through Friday (weather and temperature permitting). Our number of captures can be attributed in part to our unusually large study area.

 

Since 2008, the lab’s average capture rate has been about 1,833 birds per spring (including this season). This includes all recaps – birds caught that have already been banded – and new captures. 2017 was a record-breaking season in that the lab not only caught the most individuals in over ten springs, but also banded the most new spring migrants since 2004.

 

Why might this happen? One suggestion might be the peculiar weather pattern noted in late-April and early-May, when we noticed a few unusually cold, rainy weeks followed by a surging warm front which uncapped the metaphorical bottle containing anxious migrants stuck to our south. Perhaps a higher abundance of food, habitat options, and overall better living conditions played a part–no matter how you slice it, most if not all plausible hypotheses regarding a difference in migration from one year to the next can be attributed to climate change.

 

Our landbird conservation program has collected data on bird migration patterns during the spring and fall since 1970. (Fall banding on the property started in 1966 when the operation started under Kathleen Anderson.) What this means, most notably, is that we’ve been able to track changes in how birds migrate over nearly five decades.

 


 

Understandably, nesting is the most important aspect of a bird’s yearly routine. For migrants, making a timely arrival to their breeding grounds is crucial in claiming territory and establishing a site for set-up. Individuals arriving too late may run into a lack of available space because of the higher volume of resident species, leading to a possible dent in next year’s populations. Higher competition for food and other resources is one of the greatest plights faced by long-distance migrants. For migrants, arrival at stopover sites (like Manomet) must coincide with available insect food, or else they might not make it to the breeding grounds in time to successfully nest. Unfortunately, warmer spring temperatures lead to earlier leaf emergence and a subsequent peak of caterpillar emergence. At the banding lab, we have been monitoring migrants to be able to tease out potential mismatches in timing. Our banding data indicate that some birds are indeed arriving earlier each year, while arrival dates for other species remain consistent. Only through the continuation of our monitoring will we be able to determine if these late arrivals will eventually suffer from the climate–induced obstacles they now face. 

 

Although it’s exciting any time we break a record in the banding lab, it isn’t necessarily meaningful to compare a few years of banding data side-by-side. We saw an uptick in our numbers this year, but it wouldn’t be accurate to make the assumption that populations in general are on an increasing trend. As we’ve observed through the years, any number of factors, from weather events to insect larvae success, can attribute to how many individuals are caught from one year to the next. It is important to note that inferences made on how species are doing overall come from noticing trends over the course of several decades. While these trends point to an overall decline of migrant birds in our nets since 1970, the good news is that we’ve experienced a leveling-out period since the mid 1990’s, and perhaps even a slight growth in some species. Northern Cardinals, for example, have expanded throughout the east over the last several decades, which is likely due to milder winters and an increase in food availability along their northern range.

 

Manomet’s climate scientists (check out our Climate Services projects) and partnerships with other decision makers and research organizations have helped bolster our capacity to understand and develop new strategies to work against the effects of climate change. With new research emerging all the time, we are well on our way to help soften the impact warming temperatures have on a number of systems, from sustainable fisheries to forestry to, of course, bird conservation.

 

We pay thanks to the Manomet banding lab staff this spring for gracefully handling the booming capture rate and hot, sticky days as the season progressed.

 

The lab will re-open in mid-August for fall migration–you can follow us on social media for all the latest posts and pictures or check out our photo recap of the season on Facebook. Also, be sure to stay tuned for updates on our upcoming Birding Crash Courses this summer and fall, as well as the latest on how you can participate in this year’s Bird-a-thon in September!

2017-06-26 13:30