Start at 6:00am, closing at 12:00pm
Total 12 nets up
Total 35 birds, 13 species
- 4 Allen’s hummingbirds (Selasphorus sasin)
- 2 Hooded Orioles (Icterus cucullatus)
- 2 House Finches (Haemorhous mexicanus)
- 1 Song Sparrow (Melospiza melodia)
- 1 Spotted Towhee (Pipilo maculatus)
- 1 Black-headed Grosbeak (Pheucticus melanocephalus)
- 2 Warbling Vireos (Vireo gilvus)
- 7 Common Yellowthroats (Geothlypis trichas)
- 2 Wilson’s Warblers (Cardellina pusilla)
- 2 California Thrashers (Toxostoma redivivum)
- 1 Wrentit (Chamaea fasciata)
- 5 Bushtits (Psaltriparus minimus)
- 1 Swainson’s Thrush (Catharus ustulatus)
I arrive at Zuma around 5:40am. The temperature is nice and there is vegetation everywhere! The mustard, thistle, etc. that’s been growing since the start of spring is still there and doing well. While this means checking nets can be annoying and even painful at times with grass seeds and thistle thorns poking you constantly, we banders are still grateful for the greenery. The vast array plants that have taken root at Zuma provide wonderful bird habitat! The mustard has become so tall that it’s even attracting Red-winged Blackbirds (Agelaius phoeniceus), who normally favor marshy areas.
The rains this year have been so great, but as I learned from the master bander, even a short spell of dry climate and warm temperatures can lead vegetation to dramatically lessen. Until we reach the summer months when plants start to die off, we’re thankful the vegetation is staying around a little longer than usual.
Soon, I realize that the banders for the day were just going to be me and two other people. Knowing this, the master bander had arranged for only 12 of the usual 21 nets to be up. Four nets each, no problem! Each net run, we were bringing back two or three birds each! It was a little surprising that having only a little over half the nets we normally do, we were still bringing back an equal number of birds. Of course, we did strategically choose to set up the nets that were most productive, but 35 birds is still quite an accomplishment. Now for the details! What birds did we catch? What was so cool about this cycle?
First off, we were getting a bunch of breeding birds! This is a fantastic sign for two reasons:
- It means resident birds at Zuma have hope of getting back to pre-fire numbers
- Migratory birds like Hooded Orioles and Black-headed Grosbeaks are breeding at Zuma too!
As I’ve discussed extensively in previous blog posts, the fires of late 2018 at Zuma severely decimated the bird populations at Zuma. Some relocated elsewhere while many perished. Though it will certainly take a while for numbers to get back up to what they once were, breeding resident birds are a step in the right direction! Most of the species I list above were breeding. And if they weren’t breeding, it may have been because they were a juvenile bird!
As we are already well into the breeding season this year, we have been seeing an uptick in breeding behaviors and characteristics. Of course, we were expecting to see young birds eventually. Here they are! Hatch year (HY) birds, as they’re called, are birds that hatched during the calendar year you are in. How do we determine that we have a young bird? There are a couple characteristics!
- The nest is a dangerous place for a bird: a plethora of predators can eat you! As such, young birds will grow cheap quality feathers when they’re in the nest. These feathers are quite weak and therefore easily wear, are more tapered at the ends, and have fewer barbs (less dense). Yet, they are helpful in getting the chick get out of the nest as soon as possible.
Young birds will eventually start to replace their cheap feathers for ones that are better quality. And that brings us to… - Molt limits! Molt limits are essentially visible differences in the age of the feather. This could be the differences between worn coverts versus fresh coverts, more tapered feathers (older) versus more truncate feathers (newer). Molt limits can be quite complicated and are sometimes subtle. However, mastering the art of recognizing molt limits can greatly aid in determining the age of the bird. (I’m still working on it myself.)
Here are some young birds we caught and banded at Zuma:
The Wrentit above was the first hatch year (HY) Wrentit we have seen in a while. The species used to be the most commonly banded bird at Zuma, but after the fires of 2018, the population took a hard hit. Two weeks ago while banding, we got a breeding male Wrentit, the first Wrentit since last summer. We were hoping breeding would be successful and this young bird is proof! Yay!! While it will certainly take a while for Wrentit numbers to reach what they were pre-fire, this young bird is a step in the right direction.
The hatch year (HY) Song Sparrow wasn’t much of a surprise, but they are a great sign that conditions are suitable enough for Song Sparrows to breed successfully at Zuma. Since the beginning of spring breeding season, many birds have been found to show evidence of breeding. This could be a cloacal protuberance for males or a brood patch for females. Some males of certain species even have both (see below).
As far as resident birds go, most, if not all, adult birds are showing signs of breeding. Many are in full breeding right now! Many of the males birds’ cloacal protuberances are as large and bulbous as they can get. Brood patches are quite vascularized as fluid fills the area.
The male birds below were all found to be breeding.
The California Thrasher is a very cool species in that both males and females will incubate the nest and therefore develop brood patches. However, breeding males will also have a cloacal protuberance which serves the function of producing and storing sperm. Many species, such as the California Thrasher, are not sexually dimorphic, as in there are no apparent differences externally. As such, we normally wouldn’t be able to tell apart the male and female thrasher reliably. Thanks to breeding characteristics however, we can!
The male Spotted Towhee was also found to be breeding. Spotted Towhees are sexually dimorphic in terms of plumage, but it’s hard to tell unless you have the bird in the hand. After second year (ASY) males have a glossy black head and bright red iris. After second year (ASY) females have blackish-gray heads, throat, and underparts, uniformly brown or brownish black flight feathers, and also a bright red iris. Second year (SY) males also have similar head, throat and underpart color, but generally have darker flight feathers than the ASY female and have a gray-brown to dull red iris. Second year (SY) females have heads that are more dull black-gray and have brown flight feathers. Their iris can also be gray-brown to dull red.
The towhee down below is a second year (SY) male based on the characteristics I list above.
The House Finch below too was also found to be breeding. We were able to determine the male bird as a SY because he lacked pink edging on the median and lesser coverts and alula, had a bent tail indicating cheap feathers and therefore a young bird, and other characteristics.
Migratory species, who will be spending their time at Zuma until the early summer, have showed signs of breeding as well! When the Black-headed Grosbeak below was extracted from the net, her mate was flying around the area and watching her. The female had a brood patch, a sign of breeding. She was released after being processed and got to show off her cool metal band to her mate.
Two Hooded Orioles were caught as well, both a male and female. This was very exciting as not too many are processed (though then again, they’re only at Zuma for a short window of the year). The bold colors of the male were stunning! Even the female, though with comparatively drab colors, was still gorgeous with her yellow-olive plumage! Both birds showed signs of breeding, though we are not positive that they were a mated pair. Wishing both these species best of luck!
To add on to cool birds, guess who decided to show up again: a Common Yellowthroat who I have now processed three times! I banded the bird, who I have named Cheese, on April 9, 2022. For the next two cycles, Cheese has showed up in the net! While the band number sounds familiar every time, I am also able to recognize Cheese by his messed up toe, or should I say, absence of a part of a toe. Only the bone was showing! Cheese continues to show evidence of breeding and is doing well. Despite being caught at different nets each time, Cheese is staying in the same general area where there is abundant vegetation. We’ll see if Cheese shows up again!
In addition to birds, we also encountered quite a few other animals. Western Fence Lizards (Sceloporus occidentalis), a Southern Alligator Lizard (Elgaria multicarinata), Common Side-blotched Lizard (Uta stansburiana), Gopher Snake (Pituophis catenifer), and Two-striped Garter Snake (Thamnophis hammondii) were all spotted from the reptile department. Butterflies like Sara Orangetips (Anthocharis sara), Monarchs (Danaus plexippus), and Cabbage Whites (Pieris rapae) were observed as well. Additionally, many Stink Beetles (genus Eleodes) were seen and there was even a pair mating on one of the trails.
The master bander discovered Velvet Ants too, which are technically wasps. Velvet Ants (family Mutillidae) are known for their powerful sting. Females will locate an insect larvae (eg. caterpillars) and deposit an egg in the body. Within a week or two, the velvet ant larvae will kill the host insect from the inside. Males develop from unfertilized eggs and are therefore haploid, having only half the number of chromosomes the female has. Females, which have a full set of chromosomes, start as an egg fertilized by sperm.
Banding this cycle was amazing! We got to see so many fantastic birds! Breeding at Zuma continues and spring migrants like Hooded Orioles and Black-headed Grosbeaks are continuing their stay as well. The vegetation is still alive and well. Animals like butterflies and reptiles are abundant. Let’s see what happens next cycle!