This post is one of several on nesting birds at the Arboretum. We’re highlighting birds in our landscape as part of the 2018 “Year of the Bird”, celebrating the 100th Anniversary of the Migratory Bird Treaty Act signed by the United States, Canada, and Mexico.
Black capped chickadees are a beloved backyard fixture, common year-round resident, and the state bird of Massachusetts. Visitors can observe them at the Arnold Arboretum flitting through the branches, in flocks during the winter and in pairs during spring and summer. Earlier this spring, we installed seven chickadee tubes to provide nesting habitat for mating birds. Of these seven tubes, six were utilized by chickadees, all of which constructed nests, laid eggs, and attempted to raise their young. The following photos depict the life stages of young chickadees in several different nests.
Incubation: Once the female lays her last egg (or, in some cases, just before), she begins incubating them. Incubation is the process of warming eggs so that the embryos within them develop. To facilitate this process, the female loses a patch of feathers on her breast, called a brood patch. When she sits on the eggs her feathers part, and the bare skin of her brood patch presses upon them. This skin-on-egg contact increases the heat transfer between her body and the egg, but she still must incubate them for approximately 12 days before they are ready to hatch.
1-3 Days Old: Chickadee hatchlings, like most songbird young, are altricial (born naked and blind). This is opposed to the fully feathered and mobile precocial hatchlings of most ground nesting and aquatic birds, such as chickens, geese and ducks. From now until they leave the nest, these young birds are entirely dependent on their parents for survival. Without the adults, they will die. The new hatchlings especially require constant attention. For the first several days, the female broods to keep them warm while the male brings them food. Both parents remove their waste (conveniently contained in fecal sacks that are easily carried from the nest).
4-8 Days Old: Feathers begin to fill in along the wings, back, and tail, but patches of bare skin remain and the eyes are still closed. Growing stronger on a protein rich diet of insects, they orient themselves to maximize the opportunity to get food. They appear to have huge white and orange mouths, extending from either side of their small beaks. These are called oral flanges, and they help the adults locate and feed the young in the dark of the nest.
9-11 Days Old: Their eyes are now open and they can see the world around them. Their skin is almost completely covered by insulating feathers. The iconic black and white pattern begins to grow in. When blind, the young typically beg for food even when a human opens the tube to check on them (see the brave, hungry nestling in the previous photo). With sight comes wisdom, and they now all silently hunker down when disturbed.
12-14 Days Old: The nestlings now begin to resemble their parents. Their oral flanges are receding, their feathers have filled in, they flap their wings, noisily call for food, and perch in the nest entrance to monopolize the adults’ attention. Even at twelve days old, chickadees are strong enough to fly from the nest if a predator attacks. However, since they lack fully developed flight feathers, they would not be able to fly well or far and face starvation or predators on the ground. As a result, it is best not to visually check chickadee nestlings after they reach 10-12 days old.
That said, the nestlings in this photo are at least 14-15 days old. They were checked due to concerns that the consecutive days of wet weather in early June may have compromised the nesting tubes and put the young at risk (fortunately, it had not). Despite being bothered, all seven young in this photo remained in the tube for another few days before successfully fledging.
14-18 Days: An empty nest! One by one, young chickadees flap up to the entrance hole and then flutter out to nearby branches and shrubs. Although they can now fly short distances, they remain dependent upon their parents for food. The adults continue feeding them, somehow keeping track of this constantly moving clan. After a couple of weeks, the young chickadees have fully developed flight feathers and can find food on their own. They either fly away from their parents for good or are purposely left behind by them. Adults at this point require time to regain the strength lost from raising the young.
These juveniles face long odds. Although the average chickadee lifespan in the wild is estimated at less than 2 years, many of this year’s fledglings will not survive the next few months. However, if they learn quickly enough to avoid predators, survive disease, and live through the hard winter months to come, we may see these same birds again next spring. They will be looking for mates and nesting sites to start the process all over again.
2018 Chickadee Nest Tubes Facts
Nest tube excavation began around April 10, nest building began on April 24, and the most proactive pair of chickadees finished their nest around May 3.
The first egg was laid around May 4 while the tardiest female did not start laying until March 9.
Although seven to eight eggs per clutch was the norm, the tardy female outdid herself and laid the group high of nine.
The first hatch was around May 23 and first fledge was June 7. The tardy family’s hatch date was around May 30. All nine young birds successfully fledged on June 17.
In total, 6 pairs of chickadees used our tubes. They laid 44 eggs cumulatively, of which 30 young hatched and survived the nesting period. Look for them in our landscape this summer!