Tree Swallows are the most abundant nester. They usually contribute to about half of the total productivity on the nestbox highway. They are lovely birds that make chirping and gurgling sounds. They have a shiny blue-green backside with a white underside, and a very small bill. They like to make their nests with grasses and feathers, and lay whitish pink eggs. Feathers in swallow nests can range from as little as 2 to more than 40. The feathers Tree Swallows collect are from other species, such as mallards, mockingbirds, doves, turkeys, etc, that they find on the ground. When they are collecting feathers for building nests, sometimes tossing a feather in the air will make them swoop down to snatch it!
Very young Tree Swallow chicks have pinkish skin and not much fuzz. As they grow older they turn gray as their feather tracts develop, and then grow dark gray feathers on their head, wings, and back, and white feathers on their underside.
Western Bluebirds are our next most abundant nesters. They make “pew pew” sounds. Males have a deep rich blue color overall, with a rusty orange chest. Females are much more drab have have a light blue tinge, with a rusty orange chest as well. They like to make their nests with grasses, and sometimes add a feather or two. Their eggs are solid blue. Rarely, they may lay white eggs.
Young Western Bluebird chicks have yellow skin and some fuzz on their heads and back. When the nestlings are old enough, they can be sexed based on the shade of blue developing on their wings. Males will have a dark rich blue in their wing feathers whereas females will have a lighter grayish shade of blue (image further below). Feathered young bluebirds have spotted pattern on their chests, which will turn to smooth orange when they grow older.
House Wrens are small brown birds with a long bill. They have some barring on their tails and wings and has a pale white eyebrow. They are very quick and feisty birds and make trills and churrs, as well as loud scolding sounds when angry. Sticks are the House Wren’s main nest material and sometimes they will fill the nest all the way to the top of the box, as a way exclude competitors and predators from entering. In their nest cup they line it with small fibers and feathers to keep a soft surface for their eggs, which are cream colored with reddish brown speckles.
Young House Wren chicks have a dark gray-pink skin color and some fuzz on their head. They grow very quickly, and their feathers come in brown just like their parents’.
Ash-throated Flycatchers are the largest species that uses the nestboxes along the nestbox highway. They are brown with a yellow belly and orange tail and orange edges on the primary feathers. They are late migrants from Central America and tend to start breeding during the 2nd half of the season. Usually they find an empty box or one with an old nest, but occasionally they may nest on top of a preoccupied nest. Their nests are made of animal fur (from skunks, raccoon, rabbit etc), making their nests very soft and warm, but also stinky. They lay eggs that are whitish with red streaks.
Ash-throated Flycatcher chicks start off pink and incredibly fuzzy. As they grow older, their legs and bill grow much longer and they develop yellow feathers on their underside and brown on the head and backside. As an older nestling, they are also capable of bill-clapping like their parents when they are upset.
One of our less frequent nestbox user, the White-breasted Nuthatch, is an agile bird that can climb branches upside down. They are mostly white and gray, with a black crown in males (gray in females) and have long bills that are sightly point upward, and they make nasal-y calls and yanks. They build the base of their nest with bark, and then place some fur and feathers to make a nice cup for their eggs. Their eggs are cream colored with some light speckling.
Very young White-breasted Nuthatch chicks are pinkish-yellow, with some fuzz on their heads.
Other species that have used the Putah Creek Nestbox Highway in the past include Bewick’s Wren (left) and Oak Titmouse (middle), among a couple others. House Sparrows (right) are a non-native species, originating from Europe. Occasionally they utilize the nestboxes along Putah Creek, however we remove House Sparrow nests to prevent them from taking up space for target species.