Many bird species raise more than one brood a year

Bob Duchesne | BDN
Bob Duchesne | BDN
Eastern phoebes are among the many species of birds that are known to produce more than one brood per year.
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The woods are complicated. Right now is prime season for raising babies.
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In May, eastern phoebes claimed my porch. Per their habit, they built a nest under the eaves exactly where I come and go. She laid four eggs and sat on them faithfully for two weeks. Then the pair stuffed food into their nestlings for another 10 days. Whenever my necessary presence flushed the birds, I felt guilty.

One day, I stepped out my door, and all four nestlings panicked and fled the nest, landing momentarily in a tree at the edge of my yard. I never saw them again. At last, I could leave the house guilt-free.

The very next day, the male phoebe started calling again. Incessantly.

Really? He had finally achieved what so many weary parents have longed for — an empty nest — and he was eager to start again? His raspy serenade served to reestablish his territory and re-woo his bride for a second brood. Frankly, I thought he was nuts.

The din continued into the second day. On day three, the female was back on the nest, warming up four more eggs. OK, they’re both nuts. And I’ve lost my porch again.

Nest failure is common in all species. Many will try again after a failure. Some will try again, even after success. If conditions and the food supply allow, a few species will raise up to six broods a year. I’m talking about you, Mr. & Mrs. Mourning Dove. Bluebirds can do four. Robins can do three. Other thrushes can manage two.

Maine summers are too short to allow maximum re-brooding, but a lot of species can accomplish two broods per year. My phoebes inspired me to look up a few. For my research, I relied on www.allaboutbirds.org. The site is run by the Cornell Lab of Ornithology, and you do not get much more authoritative than that. It’s a great resource for all birders.

I looked up the warblers that are most commonly found in Bangor City Forest. Right away, I discovered a conundrum. The black-throated green warbler raises only one brood per season. But according to the website, the closely related black-throated blue warbler manages up to three. Why? There’s little difference between these two species.

I was not surprised to learn that common yellowthroats, ovenbirds and northern parulas can accomplish two broods. So can yellow, yellow-rumped, black-and-white, magnolia, pine and chestnut-sided warblers. Yet Canada, Blackburnian and Nashville warblers, which arrive and start breeding at the same time as the others, are credited with only trying once per year. Palm warblers arrive earlier and stay later than most but only manage one brood. The pair forms a bond by the end of April, and they go their separate ways as soon as the kids are gone.

Then there is the American redstart. The male is monogamous, right up until his mate is sitting on eggs. Then he may woo another female and start a second brood. Typically, he tries to feed both broods simultaneously, but researchers note that he favors the first brood if food is scarce.

The ability to raise multiple broods is undoubtedly determined by a number of factors, most of them having to do with food. For instance, the palm warbler claims boggy areas for its preferred habitat, and these sterile environments are not awash in insects. Some warblers are more likely to snatch insects out of the air, while others are more adept at gleaning food from under leaves and needles. The season for snatching flying insects is shorter than gleaning season. Flycatchers are aerial snatchers, and only two of Maine’s eight breeding flycatchers show any sign of trying to raise two broods. Besides my phoebes, yellow-bellied flycatchers of the north woods have been known to try.

Many species are constrained by Maine’s shorter season. None of Maine’s historic breeding woodpeckers has been known to raise two broods, but multiple broods are not uncommon in the southern states. Red-headed and red-bellied woodpeckers do it.

Golden-crowned kinglets rely on raising two broods per summer to make enough babies to sustain the population. But ruby-crowned kinglets raise just one and spend much of their summer working to keep those kids alive.

The woods are complicated. Right now is prime season for raising babies. Youngsters are chasing parents all over the forest. But some songbirds have started singing again recently, perhaps in hopes of re-nesting. Of these, I cherish the winter wren most. They start singing again when I least expect it, and I’ve seen the tiniest babies on Labor Day.

Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at duchesne@midmaine.com.

Watch: How to identify the songs of 5 common Maine birds


 



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