Birds don’t just eat bugs, they control their populations. We’ll also explore the “worm-like” immature insects that birds eat.
This green caterpillar is for Chickadee nestlings.
If we didn’t have birds to eat insects, we might be overrun. As predators, birds are integral to the overall ecosystem in helping keep down populations of bugs, many being destructive pests.
An entomologist (from a long time ago) made the case for the importance of birds with insect multiplication. A single female (say of a destructive moth) that lays about 300 eggs in a year, will theoretically have 6.75 million offspring by year 3!! Thank goodness for bird (and other) predators as well as parasites and diseases that prevent this from happening. Exponential insect population increases, like what we are witnessing with the Spotted Lanternfly invader, still happen though. While birds don’t respond to new invaders with their own similar population increases, healthy bird populations are important for keeping populations of bugs in balance!
A study led by Martin Nyffeler of the University of Basel in Switzerland and published in the journal The Science of Nature in August 2018 concluded that birds eat 400 to 500 million metric tonnes of bugs per year. That is about the same as the amount of meat and fish consumed by humans annually.
Birds economize when looking for food. Hunting takes a lot of time and energy, especially when there are demanding babies in the nest. Immature insects are a high protein source of food that can’t fly away! The timing of bird nesting coincides with a large diversity of insects in their larval stage.
Larvae, with many different names
Birders sometimes refer to the “worms” they see birds with. While a few birds, like robins, eat terrestrial earthworms, most of the “worms” are really insects in an immature stage. Larvae (plural of larva) is the general term for immature worm-like insects. Insects that undergo complete metamorphosis (egg, larva, pupa/ chrysalis, adult) typically have worm-like larvae. Here are some of the common names of larva:
- Caterpillar/ Inchworm – moths and butterflies
- Maggot – flies
- Grub/ Mealworm – beetles
Adults and their larvae often have a completely different body form, food sources, and even living environments. Here are examples of a fly, beetle, wasp, and moth from Pennsylvania (images not to scale).
Flower Fly (also known as Hoverfly and Syrphid)
The Flower flies mimic wasps and bees to fool predators. They easily confuse people too! As their name suggests, many of the adult species are pollinators. Recent research shows they could be responsible for up to a third of pollination. Some of their larvae species are voracious APHID eaters. They camouflage easily on flower stems, but when you do find one, you won’t have to watch for long to see it suck up an aphid!
Pennsylvania Leatherwing beetle
Adult leatherwings (aka Soldier Beetles) can be abundant on flowers where they are pollinators. They’ll walk around flowers, but are also pretty good fliers. Once they find a perch to take -off, they’ll stiffly lift their wings and fly to another flower. I find the larvae at the bottom of the wheelbarrow after transferring compost around the yard. They eat the eggs and larvae of other insects that live in decaying organic matter.
Sawfly adult and Dogwood Sawfly Larva
Sawflies have been around since the Triassic period and are related to ants, bees, and wasps. They don’t have stingers, but resemble wasps. The female uses her ovipositor to “saw” into plants to lay her eggs. Sawfly larvae are plant eaters, and many evolved to eat specific plants. I found the one in the photo on a red-twig dogwood shrub because of missing leaves. The caterpillar-like larvae can be quite conspicuous, and some are pests. There are almost 1000 species of sawflies in the US and Canada.
Isabella Tiger Moth and Woolly Bear
Sometimes the larva is better known than the adult. The Woolly Bear caterpillar is so renowned it has its own name and folklore. Supposedly, the longer the rusty-red band, the less severe winter will be. Many towns hold Woolly Bear festivals with costumes, winter prognostication, and woolly bear races. The caterpillar survives the winter despite being completely frozen. As an adult, it is the beautiful Isabella Tiger Moth.
So birds and bugs both need each other – and we in turn need them too. We can help keep this balance going by growing native plants and avoiding the use of pesticides.
Karen Campbell, a member of Lehigh Valley Audubon and FocusOnNatives.com, provided the content and images for this article.