Category Archives: HOWR

House Wrens are complicated, mysterious cheaters

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I got my start in ornithology studying the love lives of House Wrens. House Wrens pair up to raise their babies in a manner compellingly analogous to the human “nuclear family;” but, like most birds, both partners also often “cheat” on each other (i.e., copulate with other birds). This means that the male wren may have chicks in other nests besides his own, and he may end up caring for chicks that are not biologically related to him. (Note: edited. The original version of this sentence had a mistake.)

This sets up a number of interesting questions, such as: why cheat on your partner? Are the chicks sired by outside birds somehow better? Do males know when they are caring for chicks who aren’t their own? The answer to the latter question seems pretty clear (no, the males do not know), but the former two are more challenging.

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The very confused wren and the birdwatcher who noticed

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In the spring of 2015, a male House Wren and his mate built their nest inside a nestbox near a honeysuckle. His mate laid her eggs and dutifully incubated them. Then, one morning— cheep! cheep! High-pitched calls and gaping red mouths cried hungry, daddy! and the male wren was off in a paternal tizzy, collecting bugs and delivering them to his new offspring.

It was, maybe, odd that his new offspring weren’t in the nest that he had built. It was, maybe, odd that other, larger birds were also feeding his babies. It might even have been called odd that his mate was still sitting in their nest, atop whole and silent eggs. But— cheep! No time for that! The chicks were hungry!

What this male House Wren was doing, no doubt to the profound irritation of his mate, was feeding the offspring of a pair of Northern Cardinals who had nested in the honeysuckle near his nestbox.

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Double rain

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Before I studied juncos in California, I studied House Wrens in New York. Most days in the spring and summer I biked from my basement apartment to my field site, which had the no-nonsense label Unit One. The bike ride was an adventure in itself: I prepped for the field season by relearning how to stay on a bike, which I hadn’t done since childhood. (Contrary to the popular saying, it appears I can forget how to ride a bike.) On my way to Unit One I often came upon large snapping turtles stumping deliberately across the road, on the turtle-slow prowl for places to lay their eggs.

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Unit One was primarily a field site for studying Tree Swallows. The front half of it was short grass broken up by regular rectangular ponds, over which the swallows stooped and swirled. House Wren territory lay past the manicured domain of the swallows, in forest dense with brush and mosquitoes. At the start of the field season I feared getting lost in it: the paths were overgrown, and I have a poor natural sense of direction.

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One hundredth junco

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I forgot to mention in the last post: I banded my one hundredth junco a few days ago. (Well, I didn’t band him; I’m training field assistants to be able to band, so one of them banded him. But I caused him to be banded.)

Me with RROA, my hundredth junco.

Me with RROA, my hundredth junco.

We banded him RROA, which is a combination with a history: in my previous work on House Wrens, RROA was a male wren who managed to breed for three years, which was much longer than any of our other wrens. He was a bit of a celebrity. Here’s hoping that the combination brings such luck to junco RROA too.

Featured paper: fledging House Wrens are funny

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(This will be a regular feature: blurbs about papers I like.)

Today’s paper: “The process and causes of fledging in a cavity-nesting passerine bird, the House Wren (Troglodytes aedon)” by L. Scott Johnson, Robin L. Rauch, and Sara N. Dellone. Published in 2004 in Ethology 110, pages 693-705.

Fledging is the act of leaving the nest for the first time. In birds with altricial (helpless, naked, dependent) young, this is a big step: the chicks go from sitting in a nest to flying around like adult birds. Or trying to fly around, anyway. Fledglings often aren’t very good at flying at first.

A rehabbed House Wren nestling (and messy eater) nearly ready to fledge

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Fitting a bird-shaped peg through a tiny hole

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Bird wings come in a variety of shapes, from long and slender to short and rounded. These shapes affect how good the bird is at different types of flight: long and slender wings are good for soaring, while short and rounded wings are good for maneuverability.

House Wrens spend a lot of time flitting around in dense brush, so they need to be very maneuverable.

Short, rounded wing of a House Wren

(They don’t usually hold their wings that way – this was an injured bird I was caring for – but it’s the best wing-shape picture I have.)

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Auxiliary marking permit all set!

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I just got confirmation that one of my permits – to put colored leg bands on the juncos – is approved! This is awesome. Putting colored leg bands on birds allows researchers to tell individuals apart, since we can put unique combinations of colors on each bird. For example, here are the color bands of RROA, a male House Wren who lived in Ithaca:

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RROA = Red Red Orange Aluminum, with the aluminum band being the official US Fish & Wildlife band; this band has a unique number engraved on it, and all information about the bird is associated with that number. However, you have to be holding the bird in your hand to read its USF&W number, so researchers use color bands to be able to tell who is who without capturing the bird. We could identify RROA just by looking at his color bands with our binoculars – we didn’t even have to disturb him. RROA bred in our field site for three years, the longest of any House Wren there. (And yes, we called him RROA – pronounced Roe-uh.)