The Incredible Tree Swallow

They are beautiful, graceful, and elegant. They demonstrate their mastery of flight with sudden and unpredictable twists and turns. Being small and relatively quiet, they leave the viewer to wonder what bird just darted in and out of their view so quickly. The bird who embodies these descriptors is the tree swallow. These handsome aerialists are known by the scientific name Takiseneta bicolor. The word Takiseneta comes from the ancient Greek word takikinetos, which means moving quickly, and the Latin word bicolor means two-colored. Small and streamlined, these songbirds have iridescent sapphire blue backs, a white front, and a thin black mask around the eyes. As with all swallows, they have long wings, short legs, and a short bill. Their tail is slightly notched. Their feet are adapted for perching rather than for walking, so their front toes are partially joined at the base. Female tree swallows have delayed plumage maturation. In her second year, which is actually her first breeding season, the female is brown with a small amount of blue feathers. In her third year, she acquires a blue plumage that is similar to that of the male. Juveniles have dusky backs with white fronts and few, if any, blue feathers. There are a few species that are similar in appearance. The violet-green swallow has a similar white front but a green head and back and a violet-colored rump. The barn swallow has a deep blue back, buff-colored face and belly, and its most defining characteristic, the deeply forked tail. There's the cliff swallow with a reddish-brown throat, blue-capped head, and buff-colored forehead and rump. And lastly, the purple martin, who is larger than the tree swallow and is bluish-purple throughout and lacking the white belly. Tree swallows make their home in a variety of habitats, such as wetlands, grassland fields, shorelines, and wooded swamps. They prefer to live near a Being insectivores, these birds are good to have around as they provide free, natural pest control. They have small bills, strong jaws, and mouths that open wide to scoop up insect prey while on the wing. Their appetites are voracious and they can consume hundreds of insects every day. During bad weather or times of low prey abundance, tree swallows will eat plant foods such as berries. They are particularly fond of the fruits of the bayberry and wax myrtle bushes. So, what gives this bird the ability to snatch up tiny insects while flying through the air at high speeds? How in the world is it able to do that? Well, the answer is twofold. First, the tree swallow, and all swallows for that matter, have highly advanced eye anatomy. They have two fovea in each eye, whereas us humans only have one in each eye. The fovea centralis is a depression in the center of the macula where vision is the sharpest, providing visual acuity and focus for detailed tasks. It is densely packed with cone cells, which are what allow you to see color. Unlike our spherical human eyes, the eyes of swallows are longer, with the length almost equaling the width. The more tubular shape provides more room for visual acuity and doesn't compete with the brain for space inside the head. The biology of the eyes of swallows is actually similar to that of birds of prey. I noticed that when looking at a picture of them head-on, their eyes are more forward-facing than that of other songbirds whose eyes are more on the side. Compare this also to the eyes of a hawk, which are even more forward-facing. This eye position on the tree swallow likely facilitates in catching insects. They eat all kinds of flying insects, such as dragonflies, damselflies, flies, mayflies, caddisflies, true bugs, sawflies, bees, ants, wasps, beetles, stoneflies, butterflies, moths, as well as spiders, mollusks, and roundworms. Their prey can be as small as a grain of sand or as big as two inches long. Everything about their body, wing, and tail shape facilitates their ability to make incredible acrobatic twists and turns while in pursuit of their prey. During the breeding season, they also eat high calcium foods such as fish bones, crayfish exoskeletons, clamshells, and eggshells of gulls or loons. This is important for replacing calcium that was redistributed from the bones to be used for eggshell and embryo formation. The tree swallow gets its name because it nests in trees. It doesn't excavate its own nest but relies upon naturally formed tree cavities, old woodpecker holes, or nest boxes. The female does most of the nest building using grasses, pine needles, moss, plant roots, and animal hair. She may also line the nest with feathers from other birds such as geese, swans, gulls, or ducks. Tree swallows will have one to two broods per season and lay four to seven all-white eggs per clutch. Both the male and female participate in feeding the young. A feather-lined nest is always preferable. A well-feathered nest cools off much more slowly than a nest with little or no feathers, keeping the eggs and young warmer when the parents must be away. This allows nestlings to devote their energy reserve to growth and development rather than trying to keep them warm. It also gives the chicks downy soft protection as opposed to the coarse end of dried vegetation that may scratch or poke them. Studies have shown that nestlings and feather-lined nests grow faster and have a higher rate of survival than those without. White feathers are the most coveted. It isn't known for sure why they choose this color, but one hypothesis is that it makes the eggs less visible to predators. It's not uncommon for a tree swallow carrying a white feather to be pursued by another tree swallow trying to steal its feather. This sometimes results in a battle until one bird is able to get the feather back to its nest. Other times, the bird carrying a feather will let the feather drop. As it floats downward, a nearby swallow will snatch the feather and fly upward with the first bird giving chase. The two birds perform an aerial ballet for the feather that can last for minutes, sometimes with multiple swallows joining in. In this situation, it is unsure whether the behavior is play or competition. While I was in the field, I witnessed a behavior known as gaping, where an adult tree swallow will open its mouth really wide. Gaping communicates different messages depending on the situation. The first time I witnessed this was when a female sat at the nest cavity entrance with her bill wide open. In this case, it was a threat display to defend her nest while the male was away. Another time, I saw a pair taking turns bringing insects back to their nestlings. After they both had made many trips, they sat outside of the nest box and the male gaped at the female. This behavior can either mean that the male is trying to push the female away or it can be appeasement. Though I can't be totally sure, their body language suggested to me that it was a gesture of affection and affirmation of their pair bond. Nesting season coincides with the time when food is most abundant. As summer turns to fall and food sources begin to decrease, it signals to the tree swallow that it's time to head south. Fewer hours of daylight and colder temperatures demand more energy for survival and they will need the remaining food supply to fuel their long journey. When migrating, they often travel in huge flocks of 100,000 or more birds. Before settling upon their roost site at sunset, these flocks form a swirling dense cloud like a tornado of birds. With each pass, more birds descend down upon the roost as they settle in for the night. Tree swallows winter farther north than any other North American swallow and they return to the nesting grounds long before other swallows return. During cold snaps, they supplement their diet with plant foods if insect prey are scarce. Despite being one of the best studied bird species in North America, there is still little that we know about their migration and wintering habits. As I researched these birds in and out of the field, I was continually amazed at how complex their lives were. The more I learned, the more my appreciation grew. I hope that this video helped you in a similar way. Do you have a tree swallow where you live? What fact about tree swallows stood out to you? Feel free to comment down below. Thank you so much for watching and as always, happy birding!