Baby Purple Martin Feeding, Diet and Fledgling Care: What Martins Eat

How a baby purple martin develops in the nest

A baby purple martin starts life at roughly 3.0 to 3.5 grams, featherless, with closed eyelids, according to the Purple Martin Conservation Association (PMCA). It is fed by its parents from the moment it hatches, and the question of what do purple martins eat has a narrow answer: flying insects. The female lays four to six eggs on average, though a clutch can range from two to eight, and incubation lasts 15 to 16 days, delayed at times by weather. Hatching is staggered over two or three days, which means nestlings in one cavity are not all the same size.

By day 5 yellow flanges appear at the corners of the beak. The PMCA describes them as a highly visible food target for the parents. Weight peaks around day 20, often passing the parents’ own weight, and a gray neck collar shows on every nestling that age, whatever its sex. Nestlings can fledge as early as day 26, with most leaving at 28 to 30 days and a full range of 26 to 32. By week four the young come to the entrance to be fed, and the parents no longer need to enter the cavity.

For landlords, the feather length of a nestling is the best indicator of age, per the PMCA. That matters for the timing of nest checks, covered below, and for judging whether a baby purple martin lying on the ground is old enough to be out of the nest.

What do purple martins eat? The martin diet

People who ask what do purple martins eat usually expect seed or fruit. The short answer is flying insects, and only those, so the diet is the same for adults and for every baby purple martin in the nest. The Missouri Department of Conservation’s list is specific: dragonflies, damselflies, flies, midges, mayflies, Japanese beetles, June bugs, grasshoppers, cicadas, bees, wasps and flying ants. The PMCA calls martins aerial insectivores, meaning they catch and eat insects on the wing. Seed and suet are not part of that diet, so a bird feeder is not how martins are helped.

One popular belief needs correcting. The Missouri department notes that martins are day feeders, and contrary to the claim often made for them, they are not consumers of mosquitoes. Anyone installing housing as a mosquito measure is working from a myth.

The diet also explains almost every management rule that follows. A bird that eats only what flies is exposed to anything that stops insects flying: rain, snow, cool temperatures and wind. The PMCA’s hints say prolonged bad weather of that kind reduces or eliminates insect flight. Heat waves and droughts cause a different problem, because when air temperatures go above 100 degrees Fahrenheit for many days, nestlings can perish from overheating, and prolonged drought can hurt insect numbers.

Feeding purple martins in a cold snap

The PMCA names the conditions that call for supplemental feeding: temperatures below 40 degrees, steady rain, drought, dense fog and high winds. Its FAQ puts the threshold in days. When it is cool or rainy for more than three days, the birds cannot find enough food. The landlord hints say martins begin to die of starvation after four or five days, and the Missouri Department of Conservation describes rainy or cold periods longer than three or four days as capable of causing widespread death across a region. Feeding purple martins is therefore an emergency measure tied to weather, not a routine one.

Timing matters as much as the food. The PMCA reports that landlords have the most success after two or three days of non-feeding weather, when martins are hungry enough to go after the food but not yet too weak. One physical sign of trouble it gives is drooping wings, which signal that a bird’s system is breaking down.

The foods the PMCA lists are three. Crickets are kept frozen and thawed in warm water before use, and they resemble grasshoppers, a natural prey item. Mealworms come live or dried, cost less than crickets and are an excellent protein source. Scrambled eggs are cooked in a microwave or nonstick pan without added fat and broken into raisin-sized pieces; martins generally accept them once they have already learned to take crickets or mealworms. The Missouri department mentions thawed crickets, mealworms and cooked eggs offered on elevated platforms, or flung into the air with a slingshot or large plastic spoon.

How to offer food: tossing, platforms, cavities

Martins do not recognize a dish of insects as food at first. The PMCA’s feeding page describes three methods in order of use. Tossing is closest to the birds’ natural feeding habits and gets food recognized fastest. Platform feeding is a self-serve method that needs little energy, and many birds move to it after tossing succeeds. In-cavity feeding, placing insects inside the gourds or compartments, helps in extreme cold. The PMCA FAQ warns that it may take some time for martins to accept supplemental food, so the first attempt is not a failure if the birds ignore it.

Because hungry birds and a lowered house go together, the pole matters here. A housing that lowers lets a landlord check on cold-stressed birds without climbing, and a guarded pole keeps weakened nestlings safe from the predators described on the guard page.

Juvenile purple martin: fledgling care after the nest

A juvenile purple martin does not leave the nest independent, and a fledgling still depends on its parents for food. Once the young fledge, the PMCA says, they can receive care from both parents for one to two weeks. Landlords who find a fledgling or a juvenile purple martin on the ground need to ask first how old it is. The PMCA’s troubleshooting page says nestlings may fledge prematurely, before they are 26 days old, because of overcrowding, nest parasites or hot temperatures. A bird found before day 26 should go back to its original cavity or to a compartment with four or fewer similarly sized nestlings.

Nest checks have their own limit. The PMCA’s nesting page advises avoiding checks once nestlings are 22 days or older, so that they do not leave early. Weekly checks until then are the norm in the PMCA’s landlord guidance and let a landlord catch problems before they spread.

Parasites are a feeding problem in disguise, because infested nestlings do poorly. Never use pesticides in nests or boxes, the PMCA says. The safe way to reduce nest parasites is to remove the nest material and the nestlings, sprinkle one or two teaspoons of freshwater diatomaceous earth over the floor, replace the old material with clean, dry wood shavings, pine straw or dry straw, shape a shallow bowl, and put the nestlings back.

The section hub, the purple martin house guide, explains the timing of arrival and nesting that sets all of these dates.