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Bay Area Bird Blog » bird behavior

Archive for the 'bird behavior' Category

March
5th 2008
Our phoebes are back. Did they ever leave?

Posted under bird behavior & local birds

For the past few years, we’ve had phoebes in our backyard.  They’ve nested under our neighbor’s eaves, although we don’t think they’ve successfully had chicks.  In the spring and summer they’re around every day, chasing damselflies and other bugs.  I don’t recall noticing them over the winter, though they might have been around, but the past few days I’ve seen them daily so I’ve noticed them.  (I watched one of them chase down and eat a butterfly today…I know it’s the circle of life and all, but at the moment of truth I always find myself rooting for the prey.  Poor butterfly.)  Anyway, here’s my question: were they around here all winter and I just never noticed, or did they move to someplace else for the winter.  Supposedly they don’t migrate per se, but they might have been somewhere else in the neighborhood.  At any rate it’s nice to see them back.

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February
28th 2008
Pollutants’ effect on birds: yes, pollution really is bad.

Posted under bird behavior & science

Science Daily reports on research (by S. Markman et al.) that looks at birds that forage near a sewage treatment plant.  These birds are exposed to significant amounts of “estrogen mimics” and other pollutants; the Science Daily story doesn’t say, but I would guess that these are chemicals (like medications) that end up in the sewage and don’t get destroyed by treatment.  At any rate, here’s what they found: 

 birds dosed with the complete spectrum of endocrine disrupting chemicals found in the invertebrates spent longer singing, sang more often and produced more complex songs, a sexually selected trait important in attracting females for reproduction even though birds dosed at these ecologically relevant levels also showed reduced immune function. 

Of course, reduced immune function and a more complicated song might not be the only effects, but they’re ones that were obvious to the researchers.  I’m sure this has wide-ranging implications about pollutants in general, the potential implications of exposure to other species (including humans), and so on.  But my immediate thoughts are about the very specific issue of sewage.  Lots of stuff that goes down the toilet doesn’t get removed by processing.  Researchers can quantify the amount of cocaine used in a city by measuring chemical byproducts downriver from the city; many medications go right through the sewage treatment (whether they were flushed directly down the toilet, or passed through someone’s body first); flushing cat waste kills sea otters, because some parasites survive sewage treatment and infect otters.  I guess it’s worth mentioning that some chemicals in the wastewater of one city end up in the drinking water of the next city downstream, too!  

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February
21st 2008
A zillion robins, passing through

Posted under bird behavior & local birds

You could fill volumes with obvious questions I don’t know the answers to…and you could fill libraries with the answers to those questions.  One of them is: what’s up with robins?  We have some year-round in the Bay Area, but every year a bunch of migrators pass through, too, heading north from their wintering grounds in Mexico (and beyond?).  This morning, our block was filled with the chatter and tweeting of lots and lots and lots of robins — seemed like hundreds, might have just been dozens.  I assume this is a flock heading north en masse.  Some of the things I don’t know: (1) will some of them stick around, or have the robins that overwinter here already filled this area, as far as robins are concerned; (2) might some of “our” robins join a migrating flock, either headed north or next time they go south?; (3) do the robins go to and from the same places each year, or do they look for new territory on either end; (4) what is the southern edge of the robin range; (5)…I could easily list another 20 questions, just related to the migration.  But anyway, wherever they’ve been previously, lots and lots of them were in my yard this morning!

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February
18th 2008
How do birds decide where to live?

Posted under bird behavior & science

Over the years, my wife and I have watched many birds pass through our yards.  Some show up day after day; some are around for a few months in summer but not the rest of the year; some pass through and are never seen again.  We’re pretty sure that some of the regular visitors really are regular visitors: it’s the same birds showing up every year, not a different pair of phoebes (for example).  Of course it’s hard to know for sure.  At any rate, we have always wondered why some birds decide to stick around and others don’t, and how birds decide when to move along.  Well, Science Daily has a story about some research related to this issue.  It’s pretty interesting; for one thing, “the rich get richer” isn’t just a principle that applies to people:

 “The birds in the lush mangrove have access to more insects, which helps them maintain their weight,” says Studds. “This helps them to leave sooner on spring migration and arrive sooner in the more southern breeding areas, where spring is just beginning,” The birds in the dry area, however, need about another seven days to bulk up, “a long time,” says Studds. The later start means that by the time they head north, the southern breeding habitat is already taken and the birds have to keep flying, some as far north as Canada, to find the right spring conditions for breeding.

 

The Science Daily article gives a good summary, but if you want more: The study appears in the February 18 issue of the Proceedings of the National Academy of Sciences. Co-authors of the paper are Peter Marra, of the Smithsonian Migratory Bird Center, and Kurt Kyser, of Queen’s University, Ontario. 

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February
13th 2008
Crow adopts cat

Posted under bird behavior & entertainment

Here’s a video people have been sending around (thanks to my wife for passing it along to me!)  Cross-species adoption isn’t unknown — in fact, female lions have been known to adopt impala, though this always ends badly when another lion comes around for a visit — but a bird adopting a cat is a new one on me!

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February
1st 2008
Berkeley Aquatic Park planning

Posted under activism & bird behavior & local birds

Egret shading the waterThis is an egret at Berkeley’s Aquatic Park, shading the water so it can see the fish.   The City of Berkeley is considering some changes to the water flow at the park.  These changes will increase the water exchange with the Bay (that’s good: it will improve water quality in the park) but will also allow the City to dump more storm water into the park (that’s bad: water from the streets carries oil, detergents, brake dust, etc. that are bad for the environment).  The project has just started the environmental review process.  See the “activism” category if you want to get involved.

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February
1st 2008
Fickle Female Lark Buntings: some years they like this, some years they like that.

Posted under bird behavior & science

Science Daily has a summary of a Science Journal study of how female lark buntings choose their mates.  It “adds a surprising new twist to the evolutionary theory of sexual selection. Researchers at the University of California, Santa Cruz, discovered that female lark buntings show strong preferences for certain traits in the males, but those preferences change from year to year.” 

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January
30th 2008
How does an Anna’s Hummingbird chirp?

Posted under bird behavior & science

One of life’s little mysteries has been solved: the distinctive high-pitched “chirp” that a male Anna’s hummingbird can make is generated by the tail feathers, it’s not a vocal sound at all! BBC News has an article about it, with a link to the sound (worth hearing) and a poor-quality, far-away soundless video preceded by an ad (not worth watching).  By the way, this is not the chip-chip-chip sound, which is indeed a vocalization, it’s a special CHEEP that the hummingbird makes only at the bottom of a steep dive. 

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