Saturday, 7:00am-9:00am

The usual crew was out in full force this morning, chirping and sitting on the electrical cords, since fairly early in the morning. Maybe they are less likely to leave because the street is quieter on Saturday. There is, however, one couple that flies together everywhere, courting and playing each other, which I find interesting. Apparently, we're at the very end of mating season, so it's not impossible that some late bloomers are still pairing up and getting ready.

Odds are that these folks are not mates for life, but it's not entirely impossible. Carola Haas found that, while robins are not lifetime monogamists, there are some "repeat players" who meet and mate again the following year, especially if their previous mating stint had been successful. If this couple decide to mate and build a nest, even this late in the game, they'll have lots of great spots to choose from.

They'll have to consider the location pretty carefully, because predators abound (and by that I mean birds, not Spade and Archer.) I've read about an interesting experiment conducted by Ian McLean, James Smith and Glenna Stewart, who examined mobbing behavior among nesting robins. When robin couples mob nest predators, one of the unfortunate side effects is that their mobbing calls are a cue to one of their worst predators, the northwestern crow. So, robins have to balance the costs and benefits of mobbing behavior. After confirming that robins mob human "predators" similarly to crow ones, McLean et al. "mobbed" nests of the same couple during the same nesting cycle, or in subsequent nesting cycles. They found that, in the course of the same nesting effort, the robins' response is fairly constant, but across nesting cycles it changes, indicating that mobbing is not just an expression of a particular robin's aggressive character but an outcome determined by many environmental factors, including nest location. The experiment did not find a correlation between mobbing behavior and nesting success, but since the "mobbers" were the humans controlling the experiment that does not surprise me; it very well may be that, in real life, where mobbing or not mobbing has real repercussions, robins are evolutionarily programmed to mob or not mob with the potential effect of mating success in mind.

As I came to the end of today's shift, only one bird remained on the electric cords (it's a beautiful specimen with gorgeous, shiny bronze plumage on its little chest) , but the other birds, including, possibly, the couple, are not far away, judging from the chirps. At this point I can already tell the robin chirps from everyone else's, even though whenever something exciting happens in the yard or out in the street everyone emits an alarm call at more or less the same time. Even though the alarm calls are emitted to protect one's own species, they are probably taken as cues by other types of birds who then emit alarm calls of their own to their own family members.