 June-uary Made Us Shiver June 2008 left much to be desired by sunbathers, gardeners, and all those who enjoy a bare-foot romp through a field of clover. However, when I look back, I see that despite June's weather, it was a perfect month for growing birds. In the months leading up to summer I put up close to 100 nest boxes suitable for Tree Swallows or Bluebirds, and this gave me a vested interest in the bird's fortunes, or misfortunes. I watched the low temperatures of early June with some trepidation as several really cold days drove the Swallows from the our area. They returned and began to build nests in earnest. Then more cool night air put that activity on hold. This time the Swallows didn't leave but refocused attention on feeding themselves rather than on nesting and nest box activity. When the temperatures rose slightly, it was once again back to nest building. I closely watched the Swallow's activities and every cool night felt as if I was enduring it myself. At one point the weather was so un-June-like I wondered if the birds even knew what season it was. Were eggs laid and nests left unattended while the Swallows fought to save themselves? Judging from the activity around thirteen nest boxes in the yard as July begins, all of the Tree Swallows figured things out; so much so that the nestlings in each box are at or near the same state of development. I can tell this by the clamour arising from the nest boxes, a sound which suggests that next week a new crop of Swallows will be ready to take to the skies. Watching the Swallows gave me some insights into how the Mountain Bluebirds are nesting. By comparison, a nest full of Bluebirds departed a box across the road about 3 weeks ago. Why the difference? The answer is directly connected to the nature of Bluebird feeding. Let's use this spring as an example. The Mountain Bluebirds arrived at about the same time as the Swallows. The very cold weather and snow rebuffed both species first attempts to establish a foothold. A check at the 101 Mile Marsh at that time showed both species fled during a week of brutal weather. Both species returned as moderate weather returned. Then it turned cold again but this time the Bluebirds did not retreat. The inclement weather took the aerial insects out of the picture which made it imperative that the Swallows retreat to a lower elevation where such feed could still be found. Bluebirds, inveterate pouncers, could stay. Pouncers hunt for insects by sitting on a prominent post or tree then leaping to the ground to capture insects or spiders lured out by the slightest ray of sun. This is the Bluebird advantage. People have asked whether a Bluebird can hold a nest box if a Tree Swallow really has its heart set on taking over the nest box. The answer is yes. First, the Bluebird has an advantage in food gathering, as I previously described. While the Swallows will need to return southwards for lack of flying insects, the Bluebirds establish themselves and seldom have to leave a box once it is claimed. They build nests and hang on through the return of cold temperatures. By the time Swallow-friendly temperatures finally arrive, Bluebird nests are finished and their resolve to hang onto the nest box is established. Any Tree Swallow that dares to go near a Bluebird box is met with stiff resistance. Tree Swallows are no slouches when it comes to being brave of heart. They will chase Hawks and Eagles, swoop on cats and dogs and people, and take on the role of neighbourhood watchers. If for example, a Merlin appears, a rallying cry which I recognize well, goes up and the interloper is pursued relentlessly. If a Red-tailed Hawk is spotted making moves on the ground-squirrels the alarm is raised again. All manner of birds and mammals owe a debt of gratitude to the feisty Swallows. Yet, established bluebirds are quite another story. On two occasions I've watched Tree swallows make a play for a Bluebird box. In one incident the male Bluebird struck the Swallow in mid air and took it to the ground. I couldn't see exactly what happened but a moment later the Swallow broke free and fled. In another incident a male and a female Mountain bluebird, bent on claiming a box, both stood on the roof of the box and took turns leaping into the air and pursuing any Swallow that made an attempt to go to the front of the box. This combination of feeding versatility and pugnacious resolve is most likely the reason why the three boxes taken by Mountain Bluebirds at the 101 Mile Marsh last year were the same three boxes reclaimed and held by Bluebirds this year. This is kind of amazing considering that out of fifty plus boxes, Bluebirds gravitated to the exact same boxes. There is a fourth pair of Bluebirds in a box on the back fence that wasn't there last year. In reading a book on Bluebird behavior I learned that Bluebirds will not tolerate another pair of their kind in a box any closer than a few hundred feet. This box fits that bill and it probably helps that this box isn't visible from either of the nearest two bluebird-claimed boxes. One thing I will be watching for with interest after the Tree Swallow nestlings depart, is incidents of re-nesting. For some reason, a small percentage of Tree Swallows make another nest after their first brood leaves. Are these re-nesters the uber-Swallows, the super moms and dads? Already I've noticed some clustering around empty boxes by unattached Tree Swallows so I'm wondering if the re-nesters aren't re-nesters, but just late nesters – procrasti-nesters! Irregardless of why the next bunch of nests get built, I must thank June for being a good bird growing month. To e-mail Tom CLICK HERE To look at previous column CLICK HERE |
