Winter Is a Hot Time for Hawks and Other Raptors in Half Moon Bay

Unless you're on the lookout for it, you probably don't realize that right now, we've got some unusual tourists in town. Every winter, raptors (hawks and other birds of prey) converge in the fields and on the ocean bluffs around Half Moon Bay. 

On Saturday, international bird expert Alvaro Jaramillo shared his knowledge about this natural phenomenon.  Jaramillo is a local biologist, life-long birder, eco-tour guide to the Americas, and author of Field Guide to the Birds of Chile and New World Blackbirds.  His talk and the bird walk that followed were sponsored by the Coastside Land Trust (CLT), a nonprofit dedicated to protecting the open space along the San Mateo County coast, for enjoyment now and for generations to come.

Having seen birds in many parts of the world, Jaramillo spoke with experience when he said that we live in “an amazing part of the world and a really incredible region for raptors.”  He noted, by way of example, that he had taken his family to La Honda to see the snow that had fallen that morning and on the 20-mile trip he counted 60 raptors of six different species.  “In terms of hawks, falcons, and owls it’s fantastic,” he added.  “There are very few places in North America where you can see that many raptors in a short drive.”

The walk in the afternoon took participants to the local hotspot for watching raptors—a parcel of land known as Wavecrest that stretches on either side of Wavecrest Road south of Half Moon Bay, across Highway 1 from the fire station.  The open fields—a wetland this time of the year -- have tall trees where birds can roost, and an abundant rodent population, which make it a perfect habitat for raptors.  The local Sequoia chapter of the Audubon Society considers Wavecrest to be the most important wintering raptor habitat in San Mateo County, both in terms of the number of birds and the variety of species there.

CLT Executive Director Jo Chamberlain explained that the Wavecrest property is actually made up of many small lots created at the beginning of the last century when the Ocean Shore Railroad was granted the land and subdivided it.  The Peninsula Open Space Trust (POST) has purchased a large section of the property, but much of the remainder is still privately owned.  CLT is working with other agencies to acquire the remaining lots so that Wavecrest can be preserved for the public and for all the plants and animals that need it to survive.

To help participants recognize the different birds they would see on their walk later in the afternoon, Jaramillo showed slides of raptors that can be seen in Half Moon Bay or nearby and shared interesting details about their behavior and natural history, for example: 

• There are diurnal raptors that hunt in the daytime (hawks and falcons) and nocturnal raptors that hunt at night (owls).  Eagles are just big hawks, and our two eagles—the bald eagle and the golden eagle—are not even closely related, they just both happen to be great big hawks.  Falcons and hawks are also not closely related, even though they have evolved to have similar shapes, features, and behaviors.
• Specialized vision is the main thing that allows raptors to make their living—being able to see things from a great, great distance.  Jaramillo recounted that once, while watching hawks at a distance, he saw a sharp-shinned hawk suddenly dropped down right at his feet attempting to catch one of a group of sparrows feeding there.  The hawk had seen those small birds from over a mile away.
• Another amazing thing about raptor vision is that hawks that hunt voles can see ultraviolet light.  This is a great asset for the hawks because the little rodents mark their trails with urine, which reflects ultraviolet light.  The trails are like a road map for the hawks, which can easily identify an area that has a high concentration of voles by the trails they have marked.  That’s how raptors quickly find territories with plenty of food.
• Voles are related to the lemmings that live in the Arctic.  They have massive population shifts in cycles that run on average about every three years locally.  Vole populations can expand quickly because female voles can reproduce when they are only three weeks old.  Little voles make little voles and in just a few months thousands or millions of voles can appears as though out of nowhere.  This probably occurs when there is an abundance of food and low numbers of predators.  It can happen so quickly that the raptors can’t keep up with the food, but eventually more raptors come and the voles eat all the grass in the area.  Then vole numbers crash and the raptors leave and the cycle begins again.  The last real boom in the local vole population was in 2009 and before that in 2007.  When we are at the peak of a cycle here in Half Moon Bay, one sees voles everywhere.
• The white-tailed kites that come here to feed on voles and their populations follow the vole cycle.  The kites look something like gulls—immaculately white below—but their wings are more pointed, with a bit of black on their shoulders, and red eyes.  They are very social and you can often find large numbers—20 or more—sleeping together in the same tree in the evening.  When hunting, they hover or “kite” above a field, looking for prey and then dropping down to seize it.

• Northern harriers hunt by flying low, a few feet above the ground, and then dropping suddenly when they find their prey.  Unlike other hawks, the harrier relies on hearing as well as vision to hunt.  Feathers on its face are shaped in an owl-like facial disk that helps capture sound.  Because of this ability, they can hunt almost up to the time it gets dark.  They are also unusual because the male, female, and young birds all look different.  Males are gray above and whitish below, the females are brownish streaked underneath, and the young ones are solid cinnamon-colored underneath.  All can be identified by their distinctive white rump patch at the base of the tail.  Unlike any other hawk, the northern harrier males have several female mates and female harriers are more commonly seen than the males.

• Red-tailed hawks are our common, standard hawk, part of a group (genus) called buteos.  They soar up high, then sweep down on prey.  All adult red-tailed hawks have red tails, but the young have brown tails.  They all have a distinctive dark patch on the front of their wings, between the head and the “wrist.”

• The other very common local hawk is the red-shouldered hawk, which you often see perched on wires along the roadside.  They have a very different hunting strategy—they sit and wait for a lizard, frog, snake, or small rodent to appear and then swoop down on it.  They are beautiful birds, with black and white checkers on their backs, red on their heads and breasts, and a heavily banded tail.

• Earlier this winter there were two Swainson’s hawks at Wavecrest for about three weeks.  Swainson’s hawks live all over the west but previously almost every Swainson’s hawk in the world wintered in central Argentina.  As of about 20 years or so ago a few of them started to stick around in the Central Valley in the winter, and now there is a small population of them wintering there.

• The Cooper’s hawk is an accipiter—a group of hawks that make their living hunting birds by pursuit, often chasing birds through trees, maneuvering around branches and tree trunks.  They have broad wings like the buteos, but they have really long tails.  Adult Cooper’s hawks have red eyes, grayish backs and reddish fronts, a very distinctive dark cap, and round tail tips.  The species has done very well in backyards where it specifically targets doves.  They breed locally, so are here all year.

• The sharp-shinned hawk, a smaller accipiter, is mostly a winter bird locally, although they do breed in nearby hills.  They are smaller and have a square-cut tail and more rounded heads, without the dark cap of the Cooper’s.

• Two eagles are occasionally seen locally.  The golden eagle is isn’t common but can be seen in the hills, particularly from the overlook at Skylawn Memorial Park, the cemetery at the top of the hill on Highway 92.  Golden eagles feed on larger mammals like jack rabbits or even small deer.  Bald eagles, sometimes seen here, eat fish as well as other prey.

• Ospreys—the fish hawks—show up here occasionally, usually in the harbor.  The osprey is the only hawk that can dive in the water to catch fish.

• The American kestrel is our tiniest falcon.  They are relatively common on the coast in the winter, but then go inland to breed in the summer.  They hunt for voles in the winter and insects in the summer.  The males are more brightly colored than the females—with rusty back and blue-gray wings.  They hover like the kites.

• The merlin, a bird hunter, is sometimes here in the winter but not easy to find in any particular place.  They are darker and larger than a kestrel, but smaller than the peregrine falcon.

• The is the fastest creature known on earth.  Reaching speeds of over 200 miles per hour in a dive, they are masters in the air.  A pair nests on a rocky outcrop on Devil’s Slide near where the tunnel is being built.

• The short-eared owl is the signature bird of Wavecrest, though they don’t show up every winter.   They tend to come out just before night, flying slowly, almost like a butterfly.  They are not here this year, but in past 25 years or so they have been here all but three years.  Wavecrest is the best coastal wintering site for short-eared owls in California.  They are one of the few owls that can sometimes be seen flying during the day.

• Owls find their prey by hearing.  Their facial disks focus sound to their ears.  Their ears are displaced a bit so sound hits one ear at a different time than the other, allowing them to calculate the location of where the sound came from.  They can detect a difference at a 30 millionth of a second between sound arriving at one ear versus the other.  They can hunt without any light at all—"seeing" with their ears.  They can also fly silently.  Their feathers are designed to break up turbulence that would create noise when they flap their wings.

• Other local owls include the barn owl, the northern saw-whet owl (which is hard to see but breeds in Burleigh Murray Ranch park), and the (which has a really bad sense of smell and sometimes specializes in hunting skunks).

After the talk, Jaramillo, joined by Gary Deghi, another local biologist and environmental consultant, led participants on a walk from Smith Field along the trails across the muddy fields of Wavecrest.  As promised, there were many raptors there, some hunting and others perched in trees or on the coyote brush bushes that dot the field.  Seven raptor species were seen—red-tailed hawk, red-shouldered hawk, white-tailed kite, northern harrier, Cooper’s hawk, sharp-shinned hawk, and the American kestrel.

If you are interested in learning more about Wavecrest and helping to preserve it, you can participate in a Wavecrest Restoration Workday on Saturday, 26 March, from 9:45 to noon, sponsored by the Coastside Land Trust.  Volunteers will pick up trash and remove invasive plants. There will surely be raptors there to see again.