White-throated Sparrows

For today's Throwback Thursday, let's talk about the White-throated Sparrow. These sparrows breed as nearby as New York but spend winters in New Jersey on south. 

Although Dark-eyed Juncos have the "snowbird" nickname, White-throated Sparrows are also commonly seen winter visitors in my area. The Cornell Lab of Ornithology says they'll sometimes breed successfully with their Dark-eyed Junco coworkers despite not being closely related. (These kinds of remarks make me wonder how well we really know how closely related our sparrows are.)

The love lives of White-throated Sparrows have an interesting complication. They come in 2 morphs, 1 with a white stripe on their heads and 1 with a tan stripe there. These morphs are independent of sex; both males and females can be either the white-stripe morph or the tan-stripe morph. (All adults should have white throats.)

Here's where it gets complicated. Males of both morphs are attracted to white-stripe morph females, and females of both morphs are attracted to tan-stripe morph males. This means that most of the time opposite-morphs end up breeding together and thus having offspring of both morphs:

  • As much as possible, tan-striped males get together with white-striped females.
  • If there aren't enough tan-striped males, some white-striped males will get to breed with white-striped females.
  • If there aren't enough white-striped females, some tan-striped females will get to breed with tan-striped males.
  • If everyone else is paired up and there are white-striped males and tan-striped females still around, they'll settle for one another.
  • And if there's still anyone left, I guess it's time to court one of those Dark-eyed Juncos.
Here are (what I believe to be) the 2 morphs.
White-throated Sparrow - Tan-stripe Morph
January 10, 2022 at Duke Island Park
Photo 176183037, (c) jpviolette, some rights reserved (CC BY-NC)

White-throated Sparrow - White-stripe Morph
February 16, 2022 at Duke Farms
Photo 186321936, (c) jpviolette, some rights reserved (CC BY-NC)

Comments

Post a Comment

Popular posts from this blog

Northern Watersnake

Image
This April I went to Great Swamp National Wildlife Refuge with the hope (among other hopes) of seeing the Northern Watersnakes during mating season. There were 2 problems with this: I think it was slightly late in the season for this. The boardwalk trail where I had seen them in the past was partially closed due to repairs. So although I didn't see any of the 2+ intertwined snakes that I'd seen in the past, but there were still Northern Watersnakes warming themselves in the sun: April 13, 2023 at Great Swamp Photo 272117862, (c) jpviolette, some rights reserved (CC BY-NC) And here's another one coming out of the water. April 13, 2023 at Great Swamp Photo 272119139, (c) jpviolette, some rights reserved (CC BY-NC)
Read more

Female Brown-headed Cowbird

Image
Like quite a few birds, this bird is easier to identify when spotted with her significant other ; she's a Brown-headed Cowbird . Due to their tendency to be monogamous plus plain old birds-of-a-feather behavior, I usually see them with prominently brown-headed males around, greatly improving my confidence in IDing them. My understanding is that Brown-headed Cowbirds are the only obligate brood parasites in my area. Obligate brood parasites have essentially lost all their parenting skills, and thus if they were ever unable to fool other birds into raising their young, they would (almost certainly) go extinct [1]. There are, however, other brood parasites in New Jersey. These are called facultative brood parasites, and these birds will usually raise their own offspring, but will also engage in brood parasitism. (Exactly when birds perform facultative brood parasitism seems variable; one source said it occurred when resources were scarce while another said it occurred when resource
Read more

Rooftop Turkey Vultures

Image
I met these Turkey Vultures by just walking out of my apartment. (I theoretically could have gotten a picture without going outside, but that extra layer of glass can degrade picture quality a little.) Although they don't show up on these rooftops daily, they're not an uncommon visitor to my apartment complex. Similar to this spot of the woods , I wouldn't expect this to be a great place to find carcasses. I'm thinking they're here mostly because: They don't have to worry much about predators up there. They get a pretty good view of the area in case something should happen to succumb. (This apartment was near the top of a hill, providing a better view than most of the other apartments.) Since this picture was from February, it's probably a slightly warmer spot, especially near those furnace vent pipes. Although these are Turkey Vultures, it's also not unusual to see Black Vultures up there too. February 28, 2023 at Finderne Photo 264703396, (c) jpviole
Read more