Ebird Checklist: https://ebird.org/checklist/S119594884
Date: September 28, 2022
Location: Hawk Hill
Latitude, Longitude: 37.8254839, -122.4994171
Elevation: 702 ft (214 m)
Site Description: Almost 900 feet above the entrance to the Golden Gate Bridge in Marin is Hawk Hill, providing unobstructed views of San Francisco and all the surrounding areas. Because of this, the location became interesting to the US Army during World War II as engineers constructed a coastal artillery battery to protect this entrance to the Bay. But because they couldn’t protect against airstrikes, the area was quickly abandoned until the Cold War, when the top of Hawk Hill served as a radar and launch control center for the US. Close to the end of the war, all of the buildings on Hawk Hill were removed, but traces such as concrete foundations and radar pads remain today.¹ This area provides not only a great lookout but also a place for birds to stop by on their migration journeys. During fall migration, birds, especially raptors, often migrate south to reach warmer wintering grounds. Hawk Hill is an extremely popular stop on this journey because these birds avoid crossing large bodies of water. Similarly, the Headlands offer warm thermals of air that aid the birds in gaining altitude, and the geographical coastline and mountain ridges form a natural line to follow during migration. Among these birds, the most common visitors are turkey vultures, red-tailed hawks, Cooper’s hawks, and sharp-shinned hawks.² The low shrubs and hilly landscape also provide habitats for other birds such as Song Sparrows, Scrub-Jay’s, and Spotted Towhees.³ Below is a map of the topography of the area.⁴
Species Account: Merlin – Falco columbarius (Species name), Falconiformes (Order) > Falconidae (Family). These birds are small with a powerful build that is broad and stocky with pointed wings and a medium-length tail. They are generally dark overall, but their color varies geographically. There is a specific subspecies called the Taiga that is medium gray above with a pale mustache stripe and eyebrows. Both sexes are between the size of a robin or a crow and are between 9.4-11.8 in (24-30 cm) in length and weigh about 5.6-8.5 oz (160-240 g) with a wingspan of 20.9-26.8 in (53-68 cm). Adult Merlins can be gray to almost black, although females are browner. Their chests are usually streaked, and they have dark underwings and a tail with narrow white bands. These birds are strong and maneuverable fliers, and they flap their wings extremely fast. During the breeding season, they are highly territorial and are serial monogamous, and take over other birds’ nests. When courting, the males perform spectacular flight displays, although outside of the breeding season, Merlins are usually solitary. Sometimes they migrate in loose groups. Adults may be preyed on by Peregrine Falcons, Great Horned Owls, Cooper’s Hawks, and Red-tailed Hawks. These birds breed in open areas across North America and have wintering ranges that extend south as far as Ecuador. Merlins eat mostly other birds, such as the House Sparrow and other shorebirds. They attack at high speeds, chasing the prey until they tire. Sometimes they also eat large insects such as dragonflies, bats, and even small mammals. Their population has been increasing steadily over the past couple of decades, possibly due to their ability to colonize urban areas. This factor might play a role in counteracting declines caused by habitat loss in their breeding and wintering ranges.⁵
Picture from e-bird.
Picture from e-bird of flying Merlin.
Narrative: We left around 8:15 am and arrived at the location parking lot around 8:45 am. To get to Hawk Hill, we had to hike through a tunnel and up an incline to the top, where we eventually met other birders from a different organization as well. It was extremely foggy and so difficult to see anything, although we did hear a couple calls which we identified with the help of Professor’s expertise and Merlin as well. Eventually, a couple hours in, the fog lifted, and we saw an incredible amount of hawks and other birds. There were even some uncommon birds that we saw which were incredible. We left the site around 11:46 am and got back around 12:10 pm to the Koret parking lot. Overall, it was fantastic to see so many different types of hawks and soaring birds in their element. We even saw a hawk getting dive bombed and harassed by some ravens (they actually might have been crows, but I think they were ravens).
Sources:
¹ U.S. Department of the Interior. (n.d.). Hawk Hill Military history. National Parks Service. Retrieved October 4, 2022, from https://www.nps.gov/goga/learn/historyculture/hawk-hill-military-history.htm
² U.S. Department of the Interior. (n.d.). Raptors at Hawk Hill. National Parks Service. Retrieved October 4, 2022, from https://www.nps.gov/goga/learn/nature/raptors-at-hawk-hill.htm
³ Explore hotspots – ebird. (n.d.). Retrieved October 4, 2022, from https://ebird.org/hotspots
⁴ Hawk Hill Topo Map in Marin. TopoZone. (n.d.). Retrieved October 4, 2022, from https://www.topozone.com/california/marin-ca/summit/hawk-hill/
⁵ Merlin life history, all about birds, Cornell Lab of Ornithology. , All About Birds, Cornell Lab of Ornithology. (n.d.). Retrieved October 4, 2022, from https://www.allaboutbirds.org/guide/Merlin/lifehistory