Field Lab 5: Las Gallinas Valley Sanitary District

Date: 03/05/20

Location: Las Gallinas Valley Sanitary District, 38.02568°N, -122.51946°W, sea level

Site description: We began our trip at the Las Gallinas Valley Sanitary District located near the coast of the San Francisco Bay towards the east. The main trail circled three large man-made pools of water, one of which, contained a few plant covered islands. On and surrounding these islands were a plethora of aquatic bird species such as Mallards, American Wigeons, Killdeer, and various Heron species. Besides the islands, there were fairly few trees that scattered the area. Instead, massive flocks of varying bird species (primarily the Red-winged Blackbird) perched along the telephone poles that ran along the trail. To the right of the trail/ponds was a vast open field of dry shrubbery where several Northern Harriers and White-tailed Kites were spotted hunting close to the ground.

Species account: Black-crowned Night-Heron, Nycticorax nycticorax. As we approached the first pool of water, I immediately noticed several medium-sized birds on the large island perched and nestled on low-lying branches above the edge of the water. This type of perching hinted that these birds were a type of Heron as I have noticed this behavior in past excursions. I was not able to personally identify the specific type of Heron, however I was able to notice a trend in Heron behavior; this being, perching and resting under slightly sheltering plants along bodies of water. Black-crowned Night-Herons are stocky with tucked in necks that are rarely visible as well as noticeably yellow legs. Adult plumages are mainly gray with a black patch on the top of the head that extends down the back. They most commonly forage at night for fish, frogs, and other aquatic prey.

Narrative: We left USF around 8:00AM, as per usual, on Thursday, March 5th. The weather was extremely cold and gloomy, however there was minimal wind. Exiting the car I immediately heard unfamiliar calls from hundreds of black birds flying in huge flocks around the parking lot. My first guess was that these were flocks of American Crows but soon noticed that they were much smaller, had flashes of red beneath their wings, and sounded drastically different. This bird species was identified as Red-winged Blackbirds and I approximated 300 of them in the area. As we approached the first pool of water I identified an array of duck species but was not able to identify individual species besides the Mallards and American Wigeons. I quickly learned the wide variety of duck species and how challenging it is to individually categorize them. Looking down at the edges of the bodies of water I noticed a familiar bird behavior. A stout bird with long legs and an extended beak poking in and out of the shallow water made it fairly easy to identify this species as a Killdeer. At the second pool there were 3 Mute Swans floating on the surface of the water. I found this observation to be particularly interesting and had me questioning if these swans were placed in these pools by humans. 39 taxa were recorded marking this trip as having the highest number of species identified.

eBird list: https://ebird.org/checklist/S65463907



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