Like other birders and banders, I haven't been seeing much for the past week. I have banded no birds for the past three days. Perhaps we are being fooled by our lovely April weather. The migrants, however, seem to know better than to return to Minnesota before May. I checked my records from last year and found that banding did not pick up until the first of May. The plant store assures us that the average last frost for the Twin Cities is in mid-May!
So I find my thoughts drifting to Long-billed Curlews. When we taught outdoor education classes, we introduced our students to predictive morphology. By knowing the shape of a bird's bill, you might be able to predict its feeding habits. The longer the bill, especially among shorebirds, the deeper it should probe. The Long-billed Curlew does, indeed, probe deeply in the ocean mudflats where it winters.
Here is a link to an interesting website that Doug made (http://pie.midco.net/dougback/curlew.htm). I also read that Long-billed Curlews use their bills to flip cow pies in order to expose invertebrate prey!
The probing and cow pie information is from: Dugger, Bruce D. and Katie M. Dugger. 2002. Long-billed Curlew (Numenius americanus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.bnaproxy.birds.cornell.edu/bna/species/628
Friday, April 23, 2010
The last glacier stopped about 10,000 years ago just west of Northfield. During this stressful time, a population of White Trout Lilies, Erythronium albidum (right photo), mutated into the Dwarf Trout Lily, Erythronium propullans (left photo). Dwarf Trout Lilies no longer reproduce sexually. Instead they spout from single underground stems. Their flowers are smaller (dime-sized) and usually fewer petaled (4-5 pedals vs. 6 on the White Trout Lily).
If you want to see a Dwarf Trout Lily, the flowers are obviously much smaller than those of the much more common White Trout Lily. If you are in doubt, the plant is probably the White Trout Lily. The plant is a rare and endangered species, found only in Rice, Goodhue, and Steele counties of Minnesota. These photos were taken in Nerstrand Big Woods State Park near Northfield.
Why don't more plants and animals give up sex? Sex sounds like a pain in the neck. You have to brush your teeth, comb your hair, get flowers at the florist, be relatively civil. Some suggest that sex is more fun, but few have tried asexual reproduction, so I'm not sure how they could know for sure. Evolutionary biologists suggest that sex creates more genetic variation, the stuff that evolution works on, and so sexually reproducing populations have the potential to evolve quickly and successfully.
See also http://www.fws.gov/midwest/endangered/plants/dwarftro.html
Posted by Dan Tallman at 6:46 PM
Pairs of Solitary Sandpipers court, and males will chase after females. Females also fight over males. Females often begin building nests, although often the males finish the job. After the females lay their eggs, males suffer a ten-fold decrease in testosterone levels, and have high levels of proclatin. These hormones leave the males in a domestic mood, and they brood the eggs until the young hatch and are on their own. (Females will occasionally lay their eggs in other Spotted Sandpiper's nests, the young of these nests being raised by unrelated males.)
Upon laying their eggs, the females usually mate with a second male, and abandon their first mates. If the females help with incubating, brooding, or nest guarding at all, it is with her second mate. Occasionally females take on a third mate, abandoning the second. One result of all these multiple matings is that, unlike in more traditional birds, few males lack a brood. Furthermore, the sex ratio often gets skewed so that many populations of Spotted Sandpipers have more males than females.
I am not sure what is up with the Spotted Sandpiper "yawn" in the photo above. Perhaps more likely it is regurgitating arthropod exoskeletons from its gullet. Females, however, do perform a choking display when courting males. (I did not, however, see any other nearby Spotted Sandpipers when I took this photo at Sand Lake National Wildlife Refuge in South Dakota.)
My source for this blog entry is: Oring, Lewis W., Elizabeth M. Gray and J. Michael Reed. 1997. Spotted Sandpiper (Actitis macularius), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.bnaproxy.birds.cornell.edu/bna/species/289
Posted by Dan Tallman at 9:26 AM
Tuesday, April 20, 2010
Posted by Dan Tallman at 4:59 PM
Monday, April 19, 2010
At an AOU (American Ornithologists' Union) meeting in Seattle I heard about a study that showed male Eastern Bluebirds with access to more than two boxes were able to attract more than one female. As nesting locations were at a premium, the female bluebirds had better success raising young if they were attached to a wealthy real estate magnate, even if they had to share his attentions with other females. When a male's territory was plastered with nesting boxes, however, the females began bickering with each other and, consequently, their nesting success dropped. Apparently there are limits to polygamy, even among wealthy bluebirds!
Posted by Dan Tallman at 2:47 PM
Saturday, April 17, 2010
For the past two years, I have banded birds at two locations--my home in Northfield at the edge of a city park, and a large tract of land along the Cannon River near Dundas. The second site includes a large fen-like wetland.
Posted by Dan Tallman at 2:49 PM
Wednesday, April 14, 2010
I enjoy blogging because I am learning new things about birds as I write. I always knew that White-throated Sparrows come in bright and dusky morphs (the photo above is of a bright bird, the one below is a dusky one). You might be tempted to say that the bright birds are males and the dusky ones are females, but the only way to tell the sexes apart is by wing length or, in the breeding season, by cloacal condition.
Researchers have found that each morph usually breeds with its opposite type (dull males mate with bright females and visa versa). The two morphs have different chromosome arrangements. Compared with dull males, bright males are more aggressive, more territorial, and more "apt to seek matings outside the pair bond." Dusky females, on the other hand, provide more parental care than bright females. No other bird, even those with distinct morphs, share such complicated genetic, plumage, and behavioral differences.Zonotrichia albicollis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.bnaproxy.birds.cornell.edu/bna/species/128
Tuesday, April 13, 2010
Lots of Ruby-crowned Kinglets in our woods this morning. They can be identified by their small size, the nervous flicking their wings while they forage, and, in the spring, a loud, high, musical warble of clear notes--but probably not by the males' ruby crowns (which, as you can see, are usually hidden).
This winter I liked the white background in the bird portraits I took in front of snow drifts. This is my first photo using a white foam mat for background. Perhaps I've lost something by not having a natural background, but I am still impressed with the photo. I will keep trying this spring. I am disappointed not to have captured a reflection in the kinglet's eye, despite my having used the camera's flash.
Posted by Dan Tallman at 12:27 PM
Sunday, April 11, 2010
Friday, April 9, 2010
Posted by Dan Tallman at 2:52 PM
Monday, April 5, 2010
Posted by Dan Tallman at 1:18 PM
Saturday, April 3, 2010
S. H. replies: This is from a wikipedia article, not necessarily the most accurate source, but interesting anyhow. Bloodroot is one of many plants whose seeds are spread by ants, a process called myrmecochory. The seeds have a fleshy organ called an elaiosome that attracts ants. The ants take the seeds to their nest, where they eat the elaiosomes, and put the seeds in their nest debris, where they are protected until they germinate. They also get the added bonus of growing in a medium made richer by the ant nest debris.
Posted by Dan Tallman at 6:36 PM
Friday, April 2, 2010
If you look closely at this male's vent, you might notice a pink, slightly curly structure. Since I have assisted Federal duck banders, I was aware that ducks and ratities (flightless birds like ostriches and emus) are the only birds with penises. (All other birds get the job done with a cloacal "kiss," with little or no penetration.) Tonight I discovered that I am mistaken, instead of a true penis, ducks and ratites have an erectile cloacal phallus. Sperm are deposited in the male duck's cloaca and travel down the outside of the phallus. In mammals, of course, sperm travel through the penis's interior in the urethra. Thus the two structures are not homologous.
You learn something new every day; in this case from Cornell Laboratory's Handbook of Bird Biology.
Posted by Dan Tallman at 7:44 PM