Bird Watcher's General Store
Bird Watcher's General Store

How Bluebirds Decide On A Nesting Box
06/25/21


Dear Bird Folks,

Since April, weíve had a male bluebird singing from a tree in our yard. He even goes in and out of our birdhouse, chasing away any bird that gets too close. Yet, thereís no nest. What gives?

- Sharon, Eastham, MA

Iíll try, Sharon,

Iíll try to help you with your bluebird mystery, but remember to whom you are talking. When it comes to having firsthand bluebird experience, Iím not really the guy. Itís like asking me about winning an Olympic medal or how to eat barbecued ribs. I can only tell you what Iíve read. Perhaps someday bluebirds will visit my yard. And although the odds of that happening are slim, they are still better than the odds of seeing me eating barbecued ribs. Eww! How is that even a thing?

When the Europeans first arrived on these shores, they were greeted by an array of new natural wonders. Some of these wonders were undoubtedly scary, but the Eastern Bluebird wasnít one of them. Their cheery spring song helped brighten the day of all who heard it. Unfortunately, the settlers thought the bluebirds needed some company and soon brought over a number of other birds from Europe, including House Sparrows and starlings. These super-aggressive birds out-competed the bluebirds for natural nesting sites. The loss of these sites, combined with our eventual overuse of pesticides, caused a 90% drop in New Englandís Eastern Bluebird population. Then we figured it out.

Since the all-time low in the 1970s, the number of successfully nesting bluebirds has been on the rise. I would like to say the increase is due to our decrease in the use of pesticides, but that actually seems to be getting worse. What brought the bluebirds back was the installation of birdhouses. Yes, the same simple birdhouses that are made by every Cub Scout troop in America and every retired man with a basement workshop, are major factors in the bluebirdís return. Nest boxes placed in suitable habitat and made to proper specifications have helped put joy back into the bluebirds of happiness. (I know that last line was a little corny, but I needed something to help get the image of eating barbecued ribs out of my head.)

As many folks have discovered in recent years, bluebirds typically spend their winter in roving flocks, often visiting backyards in search of food (usually berries, but theyíll additionally eat scraps of suet and hulled sunflower). They also love unfrozen birdbaths, as they require extra water to help dilute any fermented berries. As the winter winds down, the birds begin to pair up for the upcoming spring. Bluebirds may look delicate, but they start their breeding process amazingly early. A few of my customers report seeing nest building activities in March. March! In case youíve forgotten, the weather around here in March is still pretty nasty, which is why most migrating birds (and many Cape Codders) havenít even returned from the south yet. But the little bluebirds donít seem to notice the weather, as they are now totally focused on mating. (I think we can all identify with that.)

Getting an early jump on the season has several advantages. The ďearly birdsĒ are able to claim the best territories, while also avoiding competition from late arrivers. Most importantly, an early start allows the bluebird couples enough time to have a second brood later in the season. This all sounds great, but if the weather doesnít cooperate, an early start can lead to nest failure, especially if the female isnít able to keep her eggs warm on cold nights. Sometimes the early bird gets the worms, but other times it ends up with eggsicles. Early nesters tend to be older couples that have reunited from the previous year. Reconnecting with the same mate saves a lot of singing, courting and searching for a new territory. But it also puts younger birds at a disadvantage. By the time the newbies get things sorted out, the better territories have already been taken and, very likely, so have the better mates. Older birds tend to have superior foraging skills, thus they sing better and look better, and consequently they can be finicky about which birds they mate with. I know choosing the most attractive mate makes them sound shallow and superficial, but I think weíd all do the same thing.

Not far from my house is a rather large public cemetery. I often stop there after work to look for birds (or to delay the trip home if I think my wife has a job waiting for me). One spring I heard the beautiful song of a male Rose-breasted Grosbeak. I immediately got excited thinking that soon there would be a grosbeak couple raising a family in one of my favorite birding spots. That never happened. It seems no females thought this maleís chosen territory (a cemetery) was a good place to raise a family. Talk about fussy. As much as the males think itís all about them, itís really all about habitat.

I suspect the bluebird singing in your yard is beginning his first breeding season, Sharon. He likely got started late, long after the females in the area had already paired up. It could also be that your yard simply doesnít provide Ms. Bluebird with what she is looking for. Just remember, when it comes to attracting birds, itís all about habitat. If, for whatever, reason bluebirds donít like our yards, itís not our fault and we shouldnít take it personallyÖat least thatís what I keep telling myself.




Artwork by Catherine Clark


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