Black-capped/Carolina Chickadee – LIFE IN THE LOWER SUSQUEHANNA RIVER WATERSHED

November 14, 2022November 14, 2022

Black-capped Chickadee Invasion

Our cute lovable chickadees are resident birds, remaining in the same general area throughout the year, often throughout their lives. In the Mid-Atlantic States, there are two species. The tiny Carolina Chickadee is at the northern limit of its geographic range in the Piedmont Province of southcentral Pennsylvania. The slightly larger Black-capped Chickadee is a year-round resident mostly to the north of the Lower Susquehanna River Watershed. Within the Susquehanna basin, an intergrade zone of the two species occurs in the mountains and bottomlands of the southern portion of the Ridge and Valley Province just to the north of the Pennsylvania cities of Carlisle, Harrisburg, and Lebanon. The range of the Carolina Chickadee, as well as the hybrid zone, has gradually crept north during the last fifty years—as much as twenty or thirty miles—while the range of the pure-bred Black-capped Chickadee has simultaneously withdrawn almost entirely from the lower Susquehanna, particularly in the valleys.

Every few years, presumably when their numbers are too great for the sustenance available from the wild food crop in their home range, Black-capped Chickadees invade the more southerly range of both Carolina Chickadees and the hybrids in the intergrade zone. This appears to be one of those years. Black-capped Chickadees are working their way south and showing up at feeding stations stocked with sunflower seeds, safflower seeds, and/or peanuts—sometimes in flocks numbering five to ten birds or more.

Let’s take a closer look at the two species…

In the Lower Susquehanna River Watershed, the Carolina Chickadee is the resident species from the Great Valley (Cumberland/Lebanon Valley) south into Maryland. — In the Lower Susquehanna River Watershed from the Great Valley (Cumberland/Lebanon Valley) south into Maryland, the Carolina Chickadee is the resident species of “tit”.

The Black-capped Chickadee is slightly larger than the Carolina Chickadee. — The Black-capped Chickadee, usually a resident of highlands to the north of the lower Susquehanna valley, is slightly larger than the Carolina Chickadee. The most conspicuous difference is the extensive amount of white in the “black-cap’s” wings, both on the edges of the flight feathers and on the set of coverts at the “shoulder”. Black-capped Chickadees often appear longer tailed and bigger headed than Carolina Chickadees and the edge of the black bib is often more ragged. The buffy wash on the flanks is usually more noticeable on the Black-capped Chickadee than on a Carolina. Hybrids from the intergrade zone, having a varying blend of characteristics, are more difficult to identify.

Not only is now a good time to carefully check the chickadees you see, but it’s an opportune time to watch for other invaders from the north, specifically the “winter fiches” including Pine Siskins, Evening Grosbeaks, Purple Finches, Red Crossbills (Loxia curvirostra), and White-winged Crossbills (Loxia leucoptera). During recent weeks, each of these species has been reported by observers at hawk-counting stations on local ridgetops, an indication that they too are experiencing inadequate food resources in their home ranges.

So, as winter approaches, you’ll want to keep an eye on those feeders—and don’t forget to keep an ear on the pines and hemlocks. The rewards could be many!

White-winged Crossbills during an invasion of the lower Susquehanna region in February 2009. Previously unnoticed in the shade, the sounds of their bills crunching the cones led to the discovery of this female (left) and male (right) among a small flock of six crossbills found feeding on Eastern Hemlock seeds at ground level.

November 28, 2020November 30, 2020

City Life: Gulls, Dabbling Ducks, and More

So you aren’t particularly interested in a stroll through the Pennsylvania woods during the gasoline and gunpowder gang’s second-biggest holiday of the year—the annual sacrifice-of-the-White-tailed-Deity ritual. I get it. Two weeks and nothing to do. Well, why not try a hike through the city instead? I’m not kidding. You might be surprised at what you see. Here are some photographs taken today during several strolls in Harrisburg, Pennsylvania.

First stop was City Island in the Susquehanna River—accessible from downtown Harrisburg or the river’s west shore by way of the Market Street Bridge.

From the middle of the Susquehanna River, City Island offers a spectacular view of the downtown Harrisburg skyline. In summer, it’s the capital city’s playground. During the colder months, it’s a great place to take a quiet walk and find unusual birds.

This Bald Eagle was in mature trees along the river shoreline near the Harrisburg Senator’s baseball stadium.

Ring-billed Gulls gather on the “cement beach” at the north end of City Island.

One of a dozen or so Herring Gulls seen from the island’s north end. This particular bird is a juvenile.

A Ring-billed Gull and some petite Bonaparte’s Gulls. Really good birders will tell you to always check through flocks of these smaller gulls carefully. It turns out they’re onto something. Look closely at the gull to the right.

A bright red bill and more of a crescent shape to the black spot behind the eye, that’s an adult Black-headed Gull (Chroicocephalus ridibundus) in winter plumage, a rare bird on the Susquehanna. Black-headed Gulls have colonized North America from Europe, breeding in Iceland, southernmost Greenland, and rarely Newfoundland.

Okay, City Island was worth the effort. Next stop is Wildwood Park, located along Industrial Road just north of the Pennsylvania Farm Show complex and the Harrisburg Area Community College (HACC) campus. There are six miles of trails surrounding mile-long Wildwood Lake within this marvelous Dauphin County Parks Department property.

A flock of Killdeer at the south end of Wildwood Lake. From November through February, a walk along the south and west sides of the impoundment can be a photographer’s dream. The light is suitable in the morning, then just keeps getting better as the day wears on.

Is this probable Carolina/Black-capped Chickadee hybrid a resident at Wildwood or just a visitor from a few miles to the north? Currently, pure Black-capped Chickadees (Poecile atricapillus) nest in the mountains well to the north of Harrisburg, and pure Carolina Chickadees nest south of the city. Harrisburg possibly remains within the intergrade/hybrid zone, an area where the ranges of the two species overlap, but probably not for long. During recent decades, this zone has been creeping north, at times by as much as a half mile or more each year. So if the capital city isn’t Carolina Chickadee territory yet, it soon will be.

Another chickadee likely to be a hybrid, this one with some white in the greater wing coverts like a Black-capped, but with a call even more rapid than that of the typical Carolina, the species known for uttering the faster “chick-a-dee-dee-dee”. It sounded wired, like it had visited a Starbucks all morning.

In the lower Susquehanna valley, Carolina Chickadees have already replaced hybrids and pure Black-capped Chickadees as nesting birds in the Piedmont hills south of Harrisburg and the Great Valley. This Carolina Chickadee was photographed recently in the Furnace Hills at Middle Creek Wildlife Management Area in northern Lancaster County. The transition there was probably complete by the end of the twentieth century. Note the characteristic overall grayish appearance of the wings and the neat lower border of the black bib on this bird,

For comparison, a bird presumed to be a pure Black-capped Chickadee photographed earlier this month in Lebanon County, Pennsylvania. This fall, “Black-caps”, like many other northern perching birds, are moving south to invade the lower elevations and milder climes of the Piedmont and Atlantic Coastal Plain Provinces. Note the extensive areas of white in the wings, the long tail, the buffy flanks, and the jagged edge of the black bib.

Along Wildwood Lake’s west shore, an adult male Sharp-shinned Hawk was soon attracted to the commotion created by bantering chickadees and other songbirds.

Yellow during the first year, the eyes of the Sharp-shinned Hawk get redder as the bird ages.

Also along the west border of Wildwood Lake, temperatures were warm enough to inspire Painted Turtles (Chrysemys picta) to seek a sun bath atop logs in the flooded portions of the abandoned Pennsylvania Canal.

And now, without further ado, it’s time for the waterfowl of Wildwood Lake—in order of their occurrence.

A pair of Wood Ducks (hen left, drake right) with American Black Ducks and Canada Geese.

A pair of American Wigeons (Mareca americana).

You just knew there had to be a booby prize, a “Blue Suede” (a.k.a. Blue Swede), a domestic variety of Mallard.

It’s a Green-winged Teal (Anas crecca) sampler. Clockwise from left: a juvenile male, a female, and an adult male.

A drake and two hen Green-winged Teal. Isn’t that great light by late afternoon?

See, you don’t have to cloak yourself in bright orange ceremonial garments just to go for a hike. Go put on your walking shoes and a warm coat, grab your binoculars and/or camera, and have a look at wildlife in a city near you. You never know what you might find.

SOURCES

Taylor, Scott A., Thomas A. White, Wesley M. Hochachka, Valentina Ferretti, Robert L. Curry, and Irby Lovette. 2014. “Climate-Mediated Movement of an Avian Hybrid Zone”. Current Biology. 24:6 pp.671-676.