Ten days ago this Black-capped Chickadee appeared at my feeder, tentatively clinging to the hanger, feathers disheveled. Black-caps maybe be common birds for many of you, abundant year-round and widespread across the continent, as you can see in the range map below. But where I live in the San Juan Islands, northwest corner of Washington state, Black-caps are unknown. I couldn’t believe what I was seeing, took photos and asked around — of my local Audubon experts, eBird, Daily Bucketeers — and its identity was confirmed.
I’m fairly certain this is one individual. I’ve never seen more than one at a time, and it departs for the woods and returns in consistent directions. How did this rare bird come here? Chickadees do not fly further than one mile across water, which is why they are not found on these islands or nearby Vancouver Island even though they are abundant on the mainland. I suspect it had the bad luck to be blown across the strait in the easterly gale winds that week, with the wind blowing and gusting over 50 mph. A chickadee weighs half an ounce.
The Daily Bucket is a regular feature of the Backyard Science group. It is a place to note any observations you have made of the world around you. Rain, sun, wind...insects, birds, flowers...meteorites, rocks...seasonal changes...all are worthy additions to the bucket. Please let us know what is going on around you in a comment. Include, as close as is comfortable for you, where you are located. Each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.
|
The rare chickadee appeared the next day at the feeder, looking better groomed and more confident. My local Chestnut-backed Chickadees noted its presence but didn’t behave any differently toward it than any of the other species foraging from the feeder.
Chestnut-backed Chickadees are abundant year-round residents in all of western Washington. They are especially well-adapted to coniferous forests for food and nesting. Black-caps prefer deciduous or mixed woods which is why they are more widespread than the Chestnuts.
Black-caps are slightly larger, with longer tails, as well as the more obvious color differences. This lone Black-capped chickadee has been visiting the feeder every day since, flying back and forth to the woods, likely caching seeds along with the other regulars, the Chestnut-backs, Red-breasted Nuthatches, juncos, towhees, finches and siskins. Occasionally however I see this chickadee standing on the perch, not feeding, but looking around at the other birds. Then it hops back around, grabs a seed and flies off.
A few days ago I heard its song. First time I’ve ever heard that distinctive chickadee-dee-dee, so different from the high-pitched chee-chee-chee of the Chestnuts. (Oh no! I just played the Black-cap song on my computer to double-check my recollection, and now I’m hearing the song in real life outside the window :( I’m so sorry little chickadee). The lone Black-cap is calling. Hoping to find others of its kind?
I can’t help but wonder what will become of this displaced bird. It is not uncommon for chickadees to hybridize between species but usually their offspring are infertile and at a disadvantage.
How is this all related to climate change?
After I began to wonder about the fate of this lone Black-cap surrounded by Chestnut-backs I looked into the chances of hybridization. I’ve found research data documenting breeding between chickadee species, but since it’s not an adaptive behavior, why do they do it? Turns out some populations of chickadees are being pushed out of their accustomed ranges by climate change, and neighboring populations are moving in, hybridizing as they occupy the area.
Chickadees are year-round residents, tightly attached to their preferred type of forest. As climate change raises global temperatures, vegetation patterns change in response. According to research performed between 2000 — 2012, a southern species, the Carolina chickadee, is moving north at the same rate as minimum-temperature limits change, pushing the resident Black-capped chickadee population north. As this report about climate change describes it,
oak-hickory forest willl be replaced by a different ecosystem...[snip]...oak forests move progressively north, forcing a compression and reduction in northern hardwood and boreal forests.
Evidence for the displacement was in the genetic makeup of nesting chickadees. Over time, southern locations in the transition zone showed a shift from hybrids to pure Carolinas, and northern spots from pure Black-caps to hybrids. It’s the female Carolinas leading the movement north.
I looked for research in the western U.S. documenting Chestnut-backed x Black-capped hybrids, since their ranges overlap in western Washington and Oregon. Found none. However I did come across a report of two Black-capped x Mountain chickadee hybrids in the British Columbia foothills of the Rockies. Mountain Chickadees are a cold climate species, living in dry coniferous forests of the upper slopes of mountains. Climate change prediction by Audubon shows their range narrowing in a higher elevation zone. Perhaps the Black-caps will displace the Mountain Chickadees altitudinally the way they are being displaced latitudinally by Carolinas in the east. Keith Russell of Pennsylvania Audubon is writing a book about change in bird ranges and makes the following longer term historical observation in this article:
In the mid-1800s, Carolina chickadees were virtually unknown in Philadelphia, and blackcaps showed up only in winter. In the 1940s, Carolinas began to breed in small numbers. In 1965, there was a population explosion, “and thereafter, the Carolina chickadee was a common resident species,” he said, and blackcaps had become rare winter visitors.
Chickadees are so closely associated with specific forest habitats that their shifts in range can be viewed as a measure of climate change. I suspect the unprecedented speed of anthropogenic climate change has overtaken the ability of chickadees to adjust their range without creating a lot of maladapted hybrids. Along with wildlife all over the world chickadees are at the mercy of runaway climate warming.
…………………..
What will become of my lone Black-capped chickadee out here on the island? I don’t know but I’ll keep watch and report any developments here at the Daily Bucket.
As alway, all nature observations welcome in the comments below. Tell us what you’re seeing in your own natural neighborhood.
"SPOTLIGHT ON GREEN NEWS & VIEWS" IS POSTED EVERY SATURDAY AT 5:00 PM PACIFIC TIME AND WEDNESDAY AT 3:30 ON THE DAILY KOS FRONT PAGE. IT'S A GREAT WAY TO CATCH UP ON DIARIES YOU MIGHT HAVE MISSED. BE SURE TO RECOMMEND AND COMMENT IN THE DIARY. |
Note: I’ll be around this morning to respond to comments and then later this afternoon and evening (I’m heading down to the city). After Christmas day, I’ll be off to the Olympic peninsula for a week, mostly out of internet range but I’ll try to check in when I can!