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.

Flight Patterns: Friday, 7am-9am

During my second hour of watching the birds today, they were not resting for long on the electric cables, but rather flying around the neighborhood and alternating short rests between the cables and the neighboring roofs. This is, to some extent, a product of how they fly.

American robin in flight
Source: whatbird.com

This is a diagram of an American robin in flight. I tried to capture footage, but they were too quick for my camera. They flap their wings very quickly and energetically and fly in a very smooth trajectory. Not a drop of energy is wasted. I've twice seen them go lower to forage. They don't dive in; they approach the insect or berry (I couldn't see what it was) diagonally, as if they were flying regularly and simply changed the angle a bit to slop downwards.

I think they need to have multiple resting points because they can't stand in place mid-air and observe their prey. The hummingbirds in the yard, who spend a lot of time around the rosebush, are much smaller in size and flap their wings to fast that the wings become invisible to the naked eye. If the robins were to attempt that, they'd fall to the ground right away; too much weight, too little speed. The solution they found was to alternate short resting points around the street and electrical cables and watch the neighborhood for predators and food. If they see a predator (like yesterday) they fly away; if they see food (like today), they adjust the angle of their flight to target it.

Apparently, robins like variety and find suburban areas such as our quiet neighborhood suitable for their needs. Joseph Howell discusses their considerations in nesting, and it seems they are not particular, and switch plans according to the environment.

Chirps in the Distance, Friday, 7am-9am

At 7am there were two robins on the electrical cords. They were fairly quiet until a few other small birds joined them. Then, everyone started singing together. I can identify six different songs, including the robin song, even though I can't see all the varieties. I can't record them, but I can try and transcribe them:

"kakakakakakaka"
"tweet tweet" (there are at least two different pitches I can here, which might belong to different varieties of birds or to two individuals of the same species.)
"papao pa, papao pa" (those are doves)
"Aa Aa Aa" (these are two syllables each, with the first syllable higher in pitch than the second one)
"pip pip pip pipipipip"
"kaaaaaaa kaaaaaaa" (each of these has a downslurring pitch)

[Aside #1: I remember having a birding guide that included similar verbal transcriptions of the bird sounds and thinking it was a fairly poor system of conveying sounds. It turns out that now people use audio pitch tracers, which can render the songs into MIDI files and then transcribe them as sheet music. That also enables them to test for frequency, volume, pitch, etc. For a place like my backyard, you'd need an editing system that would enable you to isolate the song of the particular bird from those of other birds]

[Aside #2: 20th century composer Olivier Messiaen transcribed and used actual birdsongs for his piece Oiseaux Exotiques. Very cool!]


[Aside #3: when the house predators chatter at the birds, are they trying to imitate them? The chatter pattern changes quite a bit, but since I'd been listening to it from the perspective of the cats, not of the birds, I hadn't sought a mimicry explanation. Now that I'm focusing on the birds, I should remember to pay attention in the future to what exactly it is that the predator at home is responding to.]

UPDATE: Despite there being no activity on the electric cords, I stayed until 9am and listened to the songs, which continued in the same pattern. I also noticed interesting things about flight, which I'll detail in the next post.

Songs and Chirps

American Robin
Photo credit: Christopher L. Wood

In trying to decipher the sounds I heard this morning, I looked up robin songs. This delightful page not only features better robin photos than the ones I've been able to take,  but also great recordings of their dawn and daytime songs, as well as calls to each other.

The sound tab on the website features exactly what I heard this morning. The dawn song seems louder than the day song, and the calls sound more urgent and are emitted in groups, rather than as single chirps.

What do they eat?

In trying to figure out what attracts American robins to our backyard, I've looked up some information about their diet.

According to a study done by Nathaniel Wheelwright, American robins have a very varied diet. They like fruit, but eat it seasonally; in the spring they tend to eat more insects and more variation, whereas when fruit is available they tend to stick to it.

We have berries, lemons, and tomatoes. I wonder if they're eating the berries this season.

Chirping on a Thursday Morning: 8-10am

This morning included several interesting events. It started, like every morning at Casa Corazones, with loud morning singing by the birds. I'm not sure whether the singing subsides in the later morning or the human noises drown it out. But the singing definitely changes character in response to events in the yard.

I've heard four different types of chirps today, but it's interesting that they often converge. I assume all birds need to warn their friends of a coming predator (communication) with the perhaps-unintended consequence of warning other birds, too (cue). The chirping intensified twice: when Spade got on the rosebush and when my neighbor walked her dog down the street. At that point, all the birds sounded what seemed to be a loud alarm.

This little guy positioned himself right above the fence, emitting tweets in alternating singles and pairs: "tweet, tweet tweet, tweet, tweet tweet".


He then flew up to a safer distance from the predator and continued singing, albeit with lesser frequency.

I wonder if there's a relationship between the intensity and frequency of the tweets and the proximity to the predator. And if there is one, is it linear? exponential? does the urgent chirping stop when one is at a safe distance?

After the predator got off the rosebush, the tweeter was joined by several friends. The tweets changed from the single-double pattern to a single pattern.

Then, a new pattern emerged: fast chirps in a row ("tweet-tweet-tweet-tweet-tweet") and the entire host flew away--which could be related to my neighbor's mighty Harley roaring down the street. The host relocated to a new spot on the telephone pole, but left fairly quickly.

I'm impressed with how difficult it is to find a safe resting place when you're a small bird. Everything is frightening and dangerous and you're constantly on the move, sort of like a film noir character.

(as an aside: one cabbage butterfly, two hummingbirds, one butterfly with black and orange wings, two bees.)

Welcome!

Welcome to Casa Corazones, a Marina-style home in the Mission Terrace neighborhood of San Francisco.

This blog is an assignment for my Animal Behaviour course on Coursera, in which we have to conduct wildlife observations. This blog examins the behavior of small songbirds--mostly robins--in a backyard planted with California natives and flowery bushes.

The scene:

The yard is part of a neighborhood in which people take pride in their gardens. The sidewalks are graced by a combination of established and newly-planted tree varieties, supported by the Friends of the Urban Forest program. The yard is surrounded by electric and telephone cables, which provide a habitat for the robins.

One particular activity focus is this rosebush, which is surrounded by hummingbirds and butterflies, and located right under the electric and phone cables on which the robins like to sit.

The protagonists:

The neighborhood attracts many different kinds of birds (notably robins, scrub jays, hummingbirds, and the occasional crow), several varieties of butterflies (especially cabbage butterflies), bees and moths. The water feature used to attract mosquitoes, but we have left it dry since the California drought. There are also lots of hidden protagonists: the neighborhood is full of sounds and chirps.

There are also two predators. While they are not the focus of this blog, their presence in the yard affects the birds.

Spade

Archer

Let the fun begin!