Insectivore Birds Part 1

I love the diversity of Pacific Northwest birds and insects. This is a two-part photo essay about both— Insectivore Birds. (Of course, the lovely insects are gobbled up to sustain these beautiful birds.) It’s also about the value of insects to birds in our ecosystem, and what scientists are learning about the decline of both. We’ll look at examples of insect-eating birds that evolved to forage in two different ways— on the wing and by pecking on the ground and on trees. Let’s start with aerial insectivores, the birds that mostly capture their insect prey in flight. This includes species of swallows, swifts, martins, nightjars, and flycatchers.

Local ornithologist Jackie Canterbury told me, “Eating insects is the most common pattern of eating in the bird world. Some birds eat plant material, seeds or fruits, yet almost 80% of bird families include some insects in their diet. The reason is that insects are high in proteins and fat.” In spring and summer, right here in Jefferson County we can easily observe several flycatcher and swallow species, including our largest swallow, the Purple Martin.

1. Barn Swallows prefer flies, which they catch in flight, but they eat other flying insects like beetles, bees, wasps, winged ants, and even butterflies and moths. I’ve learned that Barn Swallows usually grab fairly large insects, one at a time, rather than many tiny ones. It’s easy to photograph a Barn Swallow feeding her nestlings, like this one who built her nest above a busy porch at Fort Worden. It’s harder to photograph these aerial acrobats in flight. They tend to fly low, just above ground or water, and quite fast.

If you sit beside Chinese Gardens lagoon in early summer when swallows are flying around you, you may wonder if they are catching the flies called Non-biting Midges (Family Chironomidae).

You can see how these insects swarm beside the lagoon, and close up is one midge paused on a sign. If you’ve never heard of the Chironomidae family, you may be interested to know that globally there are about the same number of species in this family as there are bird species, over 10,000!

2. Tree Swallows are also aerial acrobats who mostly eat insects. Take a blanket and sit on the grass beside Anderson Lake, where you can watch them flying all day long in summer. When they’re feeding their babies, they frequently return to the nest boxes set up by park rangers. They consume insects of all sizes up to a two-inch long dragonfly or damselfly. (That must not include the almost three-inch long Blue-eyed Darners, among our largest dragonflies and common at Anderson Lake.) Tree Swallows usually stay within 40 feet of the ground, grabbing flies, mayflies, bees, wasps, butterflies, moths, and more. In bad weather, when prey is scarce, they can swoop down to capture other small animals like spiders and small mollusks, and even eat plants. I’ve been worried about the insectivores during this cold spring, and hope they’re finding enough nourishment.

3. You’ll see the spectacular Violet-green Swallows flying low over Chinese Gardens and Anderson Lake, as well as over the adjacent fields, feeding on flying insects such as flies, leafhoppers, aphids, beetles, and winged ants that they catch and eat as they fly. Dennis Paulson, an ornithologist who lives in Seattle, told Nan Evans in their interview on KPTZ’s Nature Now that he hasn’t seen Violet-green or Barn Swallows, “city swallows,” in Seattle in about five years. He cites the decline of nest sites and insects as the two main factors, the same factors contributing to the decline of insects worldwide due to development and agriculture that benefit humans, not insects or birds. It’s distressing to learn that U.S. Fish & Wildlife says, “Among the dramatic declines observed in birds, aerial insectivores have shown the highest percentage of species in decline of any taxonomic group: 73% of species are in decline, representing a loss of 156.8 million birds.”

4. Violet-green Swallows spend winters as far south as Mexico, but Purple Martins have the most remarkable migration— they fly here all the way from the Amazon! Our smaller swallows have a wingspan of 13.5 to 15 inches. The larger Purple Martin’s wingspan is 18 inches, allowing it to seek flying insects at higher altitudes, often 150 feet above  the ground, and even as high up as 500 feet. Jackie Canterbury said, “Research suggests that martins may feed at higher levels in the air, coinciding with air levels of the insects they consume.” They eat beetles, grasshoppers, crickets, butterflies, moths, wasps, termites, and more, also dragonflies, as in this photo.

Since there are fewer trees with holes for their “cavity nesting,” kind people have placed martin houses near water to attract them. The houses can be typical wooden birdhouses, like this one erected by Ron and Rosemary Sikes on the Port Townsend Marine Science Center’s pier. Or they can be plastic gourds, like those in the Pt. Ludlow marina.  A design favored on the East Coast, multi-level condos, are set out each year on a private dock in Mats Mats Bay, where you can pause in your kayak to watch dozens of Purple Martins swoop into the condos carrying insects to their nestlings.

5. I’ve photographed several flycatchers in summer, but not yet any who’ve just caught an insect. Near Discovery Bay, this Willow Flycatcher perches at the top of a conifer that provides a good view of flying insects. Jackie Canterbury told me that these insectivores, “rely on another strategy to catch their prey; they perch on a branch, wait for the insect to fly by, catch the insect in air, then return to the same perch. These are called ‘salliers’ and include the Tyrant flycatchers, pewees such as the Western Wood-Pewee, and kingbirds.” Flycatchers can also target insects while hovering, and then pick them from leaves. Of course, flycatchers catch flies, but also a menu of bees, wasps, ants, beetles, damselflies, butterflies, moths, and caterpillars, similar to that of the swallows above.

6. For those of us who struggle to “bird by ear,” the Olive-sided Flycatcher is a favorite, with its easily identified song that sounds just like, “quick, three beers!” The Olive-sided Flycatcher is another impressive migrant, weighing a bit over an ounce, yet able to fly up to 7,000 miles from Bolivia to Alaska. And it’s a species in decline, on what’s called the “Yellow Watch List” by the organization that tracks these numbers, Partners in Flight, estimating that numbers of the Olive-sided Flycatcher have fallen by 79% since 1970. Jackie asks, “Could it have something to do with this long migration and the need to stop over in areas with extensive deforestation or a combination of insecticides, climate change, and habitat loss?”

7. Another bird that picks insects from leaves is the Bushtit. A flock of Bushtits moves quickly through trees and shrubs looking for aphids, other tiny insects and spiders. It’s always a treat to watch them hanging upside-down to find the caterpillars and small insects that eat plants. This upright Bushtit is a female, with a pale eye.

8. This Black-capped Chickadee has an empty beak, and you may know it as a seed-eater at your bird feeder. Doug Tallamy, a professor in the Department of Entomology and Wildlife Ecology at the University of Delaware, wrote Nature’s Best Hope, an important book encouraging homeowners to convert their lawns and gardens to native habitats that will benefit native insects and birds and help slow their extinction. This fact stopped me: “… most of North America’s terrestrial bird species, some 96 percent in fact, rear their young on insects rather than seeds and berries…” and most of the nutritious food given to baby birds is caterpillars!

Tallamy explains, “While they are feeding their young, watch what the chickadees bring to the nest: mostly caterpillars. Both parents take turns feeding the chicks, enabling them to bring a caterpillar to the nest once every three minutes. And they do this from 6 a.m. until 8 p.m. for each of the 16 to 18 days it takes the chicks to fledge. That’s a total of 350 to 570 caterpillars every day, depending on how many chicks they have. So, an incredible 6,000 to 9,000 caterpillars are required to make one clutch of chickadees.” Needless to say, my husband and I dug up our scrawny little patch of lawn and planted native plants. Tallamy also recommends planting oak trees, the best host for caterpillars. We have a few in our garden, including two small native Garry Oaks.

9. The American Robin is famously the early bird who catches the worm, but as you can see, she also eats caterpillars and beetles, and feeds them to her nestlings. Robins are quite the omnivores, also consuming fruit, some snails, and they’ve been documented eating aquatic insects, shrews, and small snakes. One snow-dusted winter day near Anderson Lake I actually saw a robin attempting to eat a large treefrog. (I rescued the poor frog.)

10. Do you recognize this Red-winged Blackbird? She’s a female, and I often confuse her for a sparrow when I see her away from a wetlands and don’t notice her long, thin beak. In summer, Red-winged Blackbirds are insectivores, and in winter they turn to seeds, including corn and wheat in farmers’ fields. This Red-winged Blackbird spends summers nesting in the cattails of a wetlands on Marrowstone Island. Sometimes these birds probe at the bases of cattails and other aquatic plants to seek the insects hidden inside.

11. The White-crowned Sparrow is a bird we often encounter in our local state parks. This sparrow eats mainly seeds, but like the Red-winged Blackbird, its diet changes with the seasons. During the summer it consumes lots of caterpillars, wasps, beetles, and other insects. Obviously, these Ft. Worden White-crowned Sparrows were photographed in summer.

12. Another caterpillar connoisseur is the tiny, melodic Pacific Wren, an insectivore who eats small insects such as mites, ticks, flies, and ants, but also larger millipedes, bees and beetles. Pacific Wrens hop slowly on the ground and look for insects on decaying wood and upturned roots, then pick them off surfaces or probe into decaying bark to capture them. This Pacific Wren caught quite a large Crane Fly, a Phoroctenia vittata (Family Tipulidae).

13. Last for Part 1 is the Horned Lark, a bird I photographed with a full beak at the top of Mt. Townsend in August. Unfortunately, the angle of the sun was poor, so it’s hard to identify any of the prey, but it could include grasshoppers, beetles, and caterpillars. Horned Larks eat seeds as well as insects, but they mostly feed insects to their babies, which provide the protein they need to grow. This Horned Lark may be carrying all these insects to her nestlings. I just learned on allaboutbirds.org that Horned Larks “avoid places where grasses grow more than a couple of inches high.” They nest on the bare ground and find most of their food right on the ground, in places like Mt. Townsend, where plants grow low to the ground.

In Part 2, we’ll look at insectivore waterbirds, woodpeckers, and one hungry owl. Stay tuned!