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This spring, House Wrens nested in my bluebird box. While it wasn’t what I planned for when I put up the box, it was still cool to watch. Here is what happened.
Bluebirds Nested in Open Yards
You might think that I’d be disappointed that bluebirds didn’t choose the nestbox I put up for them, but no worries. Our yard probably has too many trees and not enough open grassy space to make bluebirds happy. After a tree fell in the back yard, it opened more space, but I still knew it was a long shot.
The bluebirds nested in boxes in other neighborhood yards with more lawn area not far away. I see them in those yards when I walk in the neighborhood. They still stop by our yard several times a day to eat dried mealworms though and are welcome when they come.
House Wrens vs Carolina Wrens
The House Wrens were a surprise, not because a different species choose the box after the bluebirds turned it down, but because we rarely see House Wrens in our yard. We’ve always played host to families of Carolina Wrens. So I was quite happy to get a chance to spend time watching a species I usually only see more briefly elsewhere.
I did initially worry that the Carolina and House Wrens might not get along but I never witnessed any conflict (which doesn’t guarantee that there wasn’t any.) The House Wrens took possession of the little corner of the yard right around the box and the Carolina Wrens took the rest. (I think the Carolina wrens nested in the tangle in the far back corner of the yard in or near the brush pile there.)
Male House Wren Starts Nest
The first House Wren activity I saw at the nest box was a long stick poking out through the entrance hole. The next day, the stick was gone. I watched the box for a while but didn’t see any movement so I carefully opened the front and I peeked in the box. There were a few more sticks piled in it. I closed it back up and sat on my back step across the yard to watch.
Periodically, I would see a little flurry of activity as a little House Wren brought stick after stick to deposit in the box. Then nothing for long periods.
House Wren males stake out a bunch of different potential nesting spots, filling each of them loosely with sticks. They also sing, hoping to attract a female to come check out the possibilities.
I’m not sure where this male’s other spots were. House Wrens are cavity nesters but can’t create their own nesting holes. So they use a cavity people or another bird (like a woodpecker) has created.
They can be quite aggressive about it apparently and this can cause problems with other cavity nesters. (They have been known to remove eggs or nestlings of rival birds or poke holes in their eggs.)
Female House Wren Takes Over Nest Building
The female House Wren looks over the male’s choices and gets the final say in which nesting cavity is actually used. Once a spot is chosen, she takes over nest building, rearranging sticks and adding various smaller bits like pine needles, feathers and grasses.
When the female was finished, the box was a little over half full of sticks with a cup lined with softer materials at the top. As you can see, she used lots of pine needles and some feathers. During this period, there was a steady back and forth between the nest box and nearby brush piles as she gathered materials.
A Quiet Incubation Period
Then it got pretty quiet. House wrens lay three to ten eggs and the female incubates them for fifteen to seventeen days. During this period, I wouldn’t see any activity for long stretches of time. Every now and then I saw her go out to feed, but otherwise you wouldn’t know the box was occupied.
Bug Catching: Feeding the Nestlings
I could tell when the eggs had hatched when I started seeing a House Wren going out to grab bugs and bring them back to the nest. House Wren nestlings stay in the nest another two weeks. As time went on, it became obvious that both the male and female were hunting for bugs and feeding the babies.
It was impressive. They were bug hunting machines. Each House Wren parent would fly out of the box, usually headed to a nearby brush pile or the log of the fallen pine tree. Within a minute or so they would grab a bug and be right back at the nest. Over and over and over again. Every once in a while they would be gone a little longer but mostly it was a constant back and forth.
Typically the parent would land on the top of the nest box with a bug in its beak and look around briefly. Then he/she would jump down to the hole and slip inside. Fairly quickly the bird parent would be right back out, often carrying a little white fecal sack to deposit a distance from the nest to keep the nest clean.
House Wren Territory
These wrens are feisty and very territorial. This pair decided that this small section of the yard (maybe fifteen feet by thirty feet was THEIR’S.) If any bird, squirrel, cat or human wandered into their territory, they complained loudly, scolding the offender until they moved on. One day when a squirrel wasn’t moving away fast enough for them, I watched one of the House Wrens diving bombing the squirrel until he did move.
This pair was not very tolerant of my presence and I usually got scolded if I was anywhere near that part of the yard. I mostly took pictures from across the yard on my back step where I usually birdwatch.
I did try sitting quietly on the ground partly behind a tree that was maybe fifteen feet away from the box for short periods. Not wanting to upset them too much, I only did that a few times.
As time went on, they did start to get more used to me (I think. At least they stopped scolding me as much.) Toward the end of their stay they would tolerate me as long as I was at least fifteen feet away and very still. I still didn’t hang around for long periods.
House Wrens & The Feeders
The House Wrens didn’t want anything from my bird feeders and I never saw them use any of the birdbaths. Even the dried mealworm feeder didn’t entice them. I only saw a House Wren in the feeder area twice.
Once one of them stopped briefly on top of each feeder. Apparently he/she didn’t find anything interesting and I didn’t see one on a feeder again. Another time, a House Wren was looking for bugs in the herb garden near the back door near where I was sitting. He/she only stayed a couple of minutes before going back to the nest box area.
House Wrens Fledge
Eventually the nestlings started getting restless. One day I watched mom and dad wren going back and forth hunting and delivering bugs. In between their arrivals, I started to see a funny little nestling face peeking out of the nest hole. I couldn’t tell if it was one bird or if they were taking turns.
Because I guessed that the young House Wrens would be fledging soon, I watched from the step for hours. I finally went inside late in the afternoon and didn’t get back out until nine-thirty the next morning.
And they were gone. Sometime later the first day or early on the second, they fledged and left the immediate area. Because they don’t use the feeders, they didn’t have as strong a need to hang around as some other species.
I’ve only seen a House Wren twice since. Once was the following day, when a House Wren briefly landed on the top of the box and then flew on. Then the next day, a House Wren briefly peeked into the box. But I have not seen them since and the only glimpse of the fledglings was the day they were peeking out of the box.
. . . until this morning! Ironically, as I was sitting on the back step writing the previous paragraph, a House Wren popped up to sit very briefly on one of the feeder shepherd’s hooks. So they are still around. Maybe the male was scouting around for his next nesting site.
Clean Out the Old House Wren Nest?
It’s a week after the babies fledged and so far I have not cleaned out the old nest. I’m a little conflicted about it. I understand that if House Wrens decide to use the same cavity again, the male will clean out the old nest, so people needn’t bother. Instead the suggestion is to clean it out at the end of the nesting season.
But what if bluebirds wanted to use the box for a second brood? Then cleaning out the box would be a good idea. Realistically though, I think my yard probably has too many trees to make a bluebird happy. And if they did decide on this box, it seems likely that could put them in conflict with the House Wrens, so I hesitate to encourage it at this point.
But just now a bluebird male flew over to the nest box and peeked inside! As much as I like to organize my yard, this is a reminder that we share space with the other creatures who live near us. They have their own minds. We don’t get to make all the decisions.
Have you had bluebirds or wrens nesting in your yard? Have you had House Wrens in your bluebird box? How did that work out? I’d love to hear about it.
Update 7/7/19: A pair of House Wrens seem to be house hunting. They were in and out of the box several times and checking out the immediate area. So it is possible another brood will be raised in the box.
Learn More About House Wrens & Nest Boxes
Learn More About Maryland Birds
See my post on Central Maryland Backyard Birds.
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