The Summer Tanager is a medium-sized songbird that breeds in the southeastern United States. Tanagers are known for their bright red plumage during the breeding season, which gives rise to their common name “Summer Tanager”. These birds build open cup nests in the branches of trees, often high up near the tops of canopy trees. The nest placement, materials, and construction provide important clues into the breeding ecology and behavior of this species. Understanding where and how Summer Tanagers build their nests can help efforts to monitor and conserve these birds.
What kind of habitat do Summer Tanagers prefer?
Summer Tanagers breed in open, mature hardwood forests across the southeastern United States. They are most abundant in oak-pine habitats, bottomland hardwood forests, and cypress swamps. Tanagers prefer forests with an open understory and a relatively closed canopy, selecting larger tracts of forest over fragmented patches. Proximity to water may also be an important factor, as many nests are built near creeks, rivers, and swamps. The dense foliage of mature forests provides security while also supporting the large insects that make up the bulk of the tanager’s diet.
What tree species do Summer Tanagers build nests in?
Summer Tanagers show preferences for certain tree species when selecting nest sites. Oaks (Quercus spp.) are the most commonly used nest trees, including species like southern red oak, white oak, water oak, and live oak. Other favored nest trees include sweetgum, blackgum, hickories, bald cypress, sycamores, elms, and occasionally pines. The large size and spreading canopy structure of mature oaks and other hardwoods provide stable nesting platforms high up in the trees. The leafy branches also help conceal the nests from potential predators.
How high off the ground are the nests usually built?
Summer Tanager nests are typically constructed high in the canopy, averaging around 16-46 feet (5-14 meters) above ground level. However, nest heights ranging from 6 feet to over 80 feet have been documented. Nests are usually built on horizontal branches well away from the main trunk. Higher nest placements likely reduce accessibility to predators and nest parasites. The height preferences may also provide some protection from severe weather. Tanagers often reuse nesting sites in subsequent years, returning to the same tree or vicinity.
When does nest building occur?
Nest building typically takes place in April and May, which corresponds with the arrival of the birds onto their breeding grounds. The female Summer Tanager does most of the nest construction, which takes 3-6 days to complete. Existing nests are often refurbished and reused from previous years. Rarely, tanagers may raise 2 broods in a single breeding season, requiring building a second nest. Peak egg laying occurs in May, so the timing of nest building is essential for successful breeding.
What materials are used to build the nests?
The nest itself is an open cup shape, composed of a range of plant materials. The outer shell of the nest is made up of dead twigs, stems, vines, and branching shoots. This coarse material is gathered from surrounding trees and understory vegetation. The inside of the nest is lined with softer fibers like dried grasses, pine needles, leaves, moss, and strips of bark. Spider silk and caterpillar cocoons are sometimes woven into the nest as well. The materials are all natural fibers collected by the female in the vicinity of the nest tree.
How are the nests constructed?
Summer Tanager nests are delicate, shallow, basket-like structures. The nests have an outer diameter of around 5 inches, with an inner cup about 2.5 inches across and 1.5 inches deep. To start construction, the female tanager weaves a loose platform of twigs and stems, anchoring it into a fork or where branches meet. Progressively finer materials are added, building up the walls to form the inner cup. The inside of the cup is then lined with soft fibers and stretchy spider silk to cushion the eggs. The architecture of the completed nest allows it to flex and conform to its placement in the canopy.
How does nest height relate to nest success?
Studies of Summer Tanager nests have examined whether height influences nest success and predation rates. In general, higher nest placements correspond to improved nest success. Nests lower in trees experience higher predation from squirrels, snakes, and other climbing predators. One 10-year study found nest success rates of just 10% for nests below 16 feet, versus 64% success for nests over 16 feet high. The improved outcome in higher nests may result from decreased accessibility as well as lower predator densities in the upper canopy.
Nest Height | Nest Success Rate |
---|---|
0 – 16 feet | 10% |
Over 16 feet | 64% |
How many eggs do Summer Tanagers lay?
A typical Summer Tanager clutch contains 3 or 4 eggs. The pale blue-green eggs are marked with brown, black, or purple spots concentrated around the wider end. The eggs measure about 0.8 inches long and 0.6 inches wide. The female lays one egg per day, until the clutch is complete. She then incubates the eggs for about two weeks before they hatch. Both parents help feed the nestlings as they grow. Just over a week after hatching, the young leave the nest as they learn to fly.
How long do the nests and eggs take to develop?
Building the nest takes 3 to 6 days. The female then lays one egg per day over a few days to complete the clutch. Incubation lasts 12-13 days before the eggs hatch. The altricial nestlings are cared for in the nest for another 7-11 days as they develop flight feathers. The nest is used for a relatively brief period during breeding, generally less than a month from completion to fledging of the young. However, Summer Tanagers frequently reuse nests for subsequent broods or return in following years.
Do both male and female Summer Tanagers help build the nest?
Nest building duties fall predominantly to the female Summer Tanager. The male may make some initial placements of sticks to start the foundation. However, the female completes the structural construction and lining of the nest. The male does assist with gathering some material that he passes along to the female. But she does the majority of weaving and shaping the nest. The female also takes the lead in choosing the nest location, while the male follows and guards her during the process.
When do the young leave the nest?
The nestling Summer Tanagers fledge about 7 to 11 days after hatching. Upon leaving the nest, the fledglings are still unable to fly very far at first. The parents continue caring for the young birds, feeding and protecting them, for a few more weeks as they learn to forage on their own. The young tanagers grow quickly and can make short flights within 2 weeks. But they do not completely separate from the adults for 25-30 days after fledging.
Do Summer Tanagers reuse nests from previous years?
It is common for Summer Tanagers to reuse old nests from prior breeding attempts. Females often choose to repair and refresh the existing nest structure rather than build a completely new nest each year. Studies show substantial nest reuse, ranging from 45-60% of nests in a given year being refurbished old nests. Returning to the same site and nest may improve familiarity and breeding success. This nest loyalty conserves the energy and resources that would be spent building a new nest from scratch.
How many broods do Summer Tanagers have in a season?
Summer Tanagers generally raise just one brood per breeding season. The entire nesting cycle from building through fledging takes about 6-8 weeks. Time constraints, energy requirements, and low clutch sizes limit most pairs to a single brood. However, cases of double brooding have been observed when conditions allow. After successfully fledging a first nest, the female may construct a second nest and lay another clutch. But two broods in one season is uncommon for this species.
Conclusion
Summer Tanagers build delicate open-cup nests high up in the branches of mature oak trees across the southeastern U.S. Nest height is important, as placement low in trees results in higher predation. Females utilize a range of plant materials to weave the nests in late spring, incubate 3-4 eggs for 2 weeks, and care for altricial young. Nest reuse is common, and pairs typically raise just one brood per season. Understanding the nesting ecology of Summer Tanagers provides insights into their breeding behavior and informs conservation efforts for this bright red songbird.