The Birding Year in the Pacific Northwest

June: Baby Birds and How They Grow

Written by Andy McCormick

Andy McCormick, Volunteer and Former Board President of Eastside Audubon

The nesting and raising of young birds varies among bird families. Baby Killdeers, Ospreys, and Spotted Towhees hatch at different stages of development and require different nurturing strategies. A baby Killdeer is independently mobile on the day it hatches. An Osprey takes months to mature. A Spotted Towhee is dependent on an adult for everything for weeks. The nesting cycles of these three birds offer insights into how many baby birds grow. The month of June begins a three-month opportunity to observe baby birds in the Pacific Northwest.

KILLDEER: Out of the Nest on Day One

Killdeers nest in the open and deposit eggs in a simple scrape in gravel. Like other shorebirds they care for four eggs, which are color-matched to the rocks making them nearly imperceptible. A Killdeer lays its eggs synchronously, that is, at the same time, and after incubation, the eggs usually hatch within eight hours of each other. Newly hatched Killdeers are precocial. They have downy plumage, are mobile, feed independently, and leave the nest in a day. They are not fed by parents and scoot around on long legs to forage on their own. During this period, they are at risk from predators because they are flightless for up to three weeks.

Adult Killdeers are very protective of their independent young. They allow the young to forage within a defined area. I have observed adults which post themselves as sentries at opposite sides of the space they allocate for the young. If the young Killdeers are threatened by another bird, or a mammal including a human comes too close, the adults perform an elaborate distraction display of alarmed calling, flying about, or faking a broken wing and spreading their tail in a show of vulnerability to distract the intruder. Within 17 to 20 days a young Killdeer molts into a juvenile plumage and begin to look like a small adult.

OSPREY: Slow to Grow

Ospreys build a large stick nest in the open at the top of a tree, or frequently today, on a platform provided for them by humans. Osprey chicks hatch in early to mid-June with downy feathers and dependent on the parents. The adult female generally stays with the chicks roosting and feeding them. The male hunts for fish. When the male returns to the nest both the female and the chicks break into loud calling as they anticipate the male dropping a fish into the nest. The female grabs the fish and vigorously pulls it apart in order to directly feed the young by placing chunks of fish into each chick’s open mouth.

Ospreys are large birds, and it will take weeks before the young are strong enough to pull meat off a fish. As consequence, the parental feeding pattern continues in a regular rhythm for about 50 days until early August when the young fledge from the nest. Even as they increase their independent activity, young Ospreys remain at the nest, roosting at night, and eating fish left by the adults. They may remain until mid-September before departing for fall migration.

An Osprey lays eggs sequentially, usually one to three days apart. The eggs will also hatch in sequence. As the young birds mature sibling rivalry becomes more apparent. The first hatchling can become dominant in the nest and will be the most active in taking food from the parent; it will go after the whole fish before other chicks try to; and it may fledge first. I have observed a dominant young Osprey take a newly deposited fish from the nest, fly away with it to a nearby tree, and eat it. If another young Osprey tries to try to get some of the fish, the first bird will defend it. In this way the sequential laying and hatching of eggs is likely to produce a minimum of one strong and aggressive raptor which may have a higher incidence of long-term survival.

SPOTTED TOWHEE: Helpless for Weeks

In the manner of many perching birds (passerines) towhees hatch atricial, that is defined as helpless and fully dependent on adult care. They must be fed by an adult which brings food items back to the nest. Young birds require protein which is usually sourced from insects. Within a few days of hatching feather shafts break through the baby bird’s skin. These first feathers soon produce a drab, grayish-brown cryptic juvenile plumage. This feather molt occurs quickly. Because of their fast growth, these initial feathers are weaker than adult feathers, but they get the young bird off on its life.

This first plumage lacks adult coloration and provides these ground-feeding birds with some camouflage protection from predators. It also makes the identification of young Spotted Towhees more difficult. At this time of year looking at a bird’s structure and behavior will help with identification. Once this plumage is in place, which takes about three weeks, the young towhee can fly.

However, these first feathers are temporary and birds like towhees will undergo a second molt in September or October and adopt their first basic plumage. Birds in other families may wait until early spring for their first basic plumage molt.

FEEDING STRATEGIES VARY

Understandably, getting fed is an important part of everyday life for a new bird and they are equipped with behaviors to attract the adult’s attention to get fed. For example, young crows and gulls are quite vocal with incessant begging calls as they closely follow the adult birds. In addition to begging calls, smaller birds will employ rapid wing flaps to attract the parent’s attention. They will follow the adult and repeatedly move closer and flap their wings. Both Black-capped and Chestnut-backed Chickadees readily use wing flapping to beg for food.

Bald Eagles capitalize on an eaglet’s desire to be fed to prompt them to fly. By reducing the frequency of feeding and stopping at some distance from the nest, the adult eagle uses the food as a lure to entice the young bird to fly to them to get their meal. As the juvenile bird gets stronger, the adult will stay farther from the nest forcing longer flights by the young bird. The adult will also stop breaking up the food.

In June, the excitement of bird migration is replaced by the quiet activity of adults raising young birds. It is a part of birding that is well worth our attention.

SUGGESTIONS FOR FURTHER READING

Hanson, Thor (2011). Feathers: The evolution of a natural miracle. New York: Basic Books. Evolution, temperature regulation, protection, and color are some of the aspects of feathers covered in this volume.

Hill, Geoffrey E. (2010). National Geographic Bird Coloration. Washington, DC: National Geographic Society. This book offers a review of color in the stages of bird plumage, environmental effects on color, feather change from wear and the ultraviolet rays of the sun, and sexual aspects of color in birds.

Howell, Steve N.G. (2010). Molt in North American birds. Boston: Houghton Mifflin Harcourt. This book is out of print, but it is worth finding. This deep dive into the sequence of the growth of feathers is comprehensive and covers all bird families. Howell’s revision of the Humphrey-Parkes approach to the molt sequence is used by bird banders and biologists.