Tree Swallow (Tachycineta bicolor) lives in open wet areas across North America, Mexico, Central America, Caribbean. Its conservation status is Least Concern.
Fascinating facts about the Tree Swallow
- Tree swallows are generally socially monogamous, yet about eight percent of males mate with more than one female, showing a notable level of polygyny. This deviation occurs alongside unusually high rates of extra-pair paternity within the species. Although extra-pair matings can benefit males, the female controls copulation, leaving the advantage to females unclear. The combination of social monogamy and occasional polygyny makes their breeding system distinctive.
- During its autumn migration, a tree swallow typically spends an average of 57 days at stop-over sites to refuel before reaching its wintering grounds. It may travel along any of three main flyways - Western, Central or Eastern - depending on its breeding location. These pauses are crucial for maintaining the energy needed for the long journey to coastal and tropical winter habitats.
- Only about 14% of female tree swallows and 4% of males change breeding sites each year, indicating strong site fidelity. Most birds that do disperse remain within 10 km of their previous nest, showing limited movement across the landscape. Dispersal rates rise when breeding fails; roughly 28% of unsuccessful females relocate compared with just 5% of successful ones. This pattern of low but conditional dispersal helps maintain stable local populations.
- The entrance of a tree swallow's nest cavity is usually only four to five centimetres across, a dimension that keeps many predators from reaching the eggs or chicks. Openings can vary in height, with recorded ranges from 3.5 to 26 centimetres. Most cavities hold less than 1,000 cubic centimetres of space, further limiting access. By selecting such narrow entrances, the birds increase the safety of their brood.
- In natural cavities tree swallows place their nests about 27 metres from the nearest neighbour, a spacing that lessens direct competition and lowers predation risk. The holes are on average 3.4 m above the ground, though almost half are situated under 2 m. Higher cavities are preferred because they reduce the chance of predators reaching the nest, while lower sites may be chosen to avoid competition with other birds.
Sources
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At a glance
RangeNorth America, Mexico, Central America, Caribbean
HabitatOpen wet areas
DietInsects and spiders
About the Tree Swallow
As the sun rises over the wetlands, a flurry of iridescent feathers bursts forth from the nesting boxes, as Tree Swallows take to the skies with an effortless elegance, their slender bodies darting and weaving with precision through the air. With a mesmerizing fluidity, they pursue the insect throngs that dance above the marshes, their forked tails streaming behind them like tiny banners. In this whirlwind of motion, the Tree Swallow embodies the very essence of aerial acrobacy, a true marvel of evolutionary adaptation.
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Tree Swallow photographed on Feravox
