Spring is breeding season for birds, and it shows. They're wearing their brightest plumages, they perform crazy courtship displays and sing beautiful songs, and when they've found mates, they begin building nests to raise their babies.
Watching a bird build a nest is pretty magical. Some birds weave strands of grass together. Others scoop up bits of mud in their beaks and glue their nests to ledges or houses. Some, including Acorn Woodpeckers, lay their eggs at the bottom of hollowed-out tree cavities. Regardless of how exactly they build their nests, many birds spend a lot of time on them, making them as cozy, sturdy, and safe as possible in order to safely raise their babies.
Time for the tenuous connection to my own life. Unlike the birds, I am not preparing to mate and raise babies this spring. But I have spent the past couple weeks settling in to a new place, organizing and re-organizing my space to make it my own, and delighting in the spring weather and the antics of the breeding birds all around me. Since mid-March, I have been living at Hastings Natural History Reservation in Carmel Valley, California. I'm working here as a field tech on a long-term study of Acorn Woodpeckers, and I'll be here until July.
It's beautiful here. The habitat is mostly oak savannah, which means oak trees interspersed with grassland, chaparral, and other open habitat. In other words, acres and acres of rolling hills that look like this:
To an easterner, one of the most striking things about this landscape at this time of year is the wildflowers.
To an Acorn Woodpecker, this landscape is home.
In general, a woodpecker makes its living by pecking wood. Most woodpeckers peck at trees to extract the insects living in the wood. Others, like sapsuckers, make little holes deeper into the tree and drink the sweet xylem sap, or eat the insects that are attracted to the sap. Woodpeckers also use their tree-pecking skills to excavate larger holes, or cavities, which they use for roosting (sleeping at night) and, during the breeding season, for nesting in.
But Acorn Woodpeckers don't stop there. No. Acorn Woodpeckers take woodpecking to another level. In the fall, they drill acorn-sized holes into tree bark, dead branches, or even house siding and store acorns in the holes, making "granary" trees that provide them with a food source through the winter and spring, when there are no acorns to be found. They also eat bugs, tree pollen, and various other things, but acorns are their staple.
So what am I actually doing here?
People have been studying Acorn Woodpeckers at Hastings for decades, and every season there are a few different scientists researching different aspects of the Acorn Woodpeckers' social interactions.
Why are Acorn Woodpeckers so interesting? They have a very complicated social structure. They live and breed on discrete, defined territories, in groups, not in simple pairs like most birds. The breeders in a group can be just a male/female pair, or they can be a polygynandrous group of a few males (usually brothers or closely related) and a few females (usually sisters or closely related, but unrelated to the males). This means that babies raised together might be siblings, half-siblings, or cousins.
To make things even more complicated, the breeding woodpeckers in each group are assisted by "helpers," offspring from previous years who stick around and help to raise their younger siblings or cousins, even though they don't breed themselves.
This system raises lots of questions from an evolutionary perspective. For example,
There's a lot of complicated evolutionary biology happening here. But as a field tech, I'm doing the dirty work. Right now, there are a few main things I'm doing.
1. Censusing woodpecker territories. We have a list of all the individual birds that are known to be part of each group. But we have to update that list periodically because sometimes birds die, sometimes they move away to other groups, sometimes new woodpeckers join a group, etc. So I conduct three-hour watches at a given territory and try to identify as many woodpeckers as possible. When I determine that a certain bird is still in that group, I update the list with the date it was last seen.
But how do you tell the birds apart??? They all look the same.
The majority of the population of Acorn Woodpeckers at Hastings is color banded, meaning each bird wears several colored leg bands that can be read through a spotting scope to identify the bird in the field. Here is a photo of a captive Acorn Woodpecker named Almost showing off two of his color bands. Almost lives with Natasha and is missing part of his wings, so he can't fly. He can certainly climb, though, and he can make holes and eat acorns. So life is pretty good.
It's pretty easy to read Almost's color bands in this photo, but imagine trying to read bands on a bird that's a lot farther away, moving around on a tree all the time, and often sitting on its feet and fluffing up its belly feathers. It's challenging. But reading color bands is also very rewarding when you get it right, because then you can be certain that you're looking at a specific individual bird.
The artist in me loves reading color bands because of, well, the colors.
Red Orange Yellow Light Green Forest Green Dark Green Light Blue Medium Blue Dark Blue Mauve Light Pink Bright Pink Dark Pink Brown Gray Black White
They can be combined in many different ways. Bands can be a solid color, split (like the bands on Almost's right leg), or narrow striped (narrow stripes of two different colors, repeating along the band). Sometimes the color combinations can be frustratingly hard to read, like if a bird's leg is Light Blue-Light Green/Light Green-Light Pink. In bad light, those colors all look the same. But other times the colors stand out beautifully, like one bird whose left leg was Yellow/Orange and looked like a flash of sunlight when she took off from a branch.
When I'm able to read two or more of a bird's color bands, I write down the colors on a data sheet, along with information like the date, time, species name, and the specific territory that I'm censusing. I also write down the sex of the bird, which is very easy to determine in Acorn Woodpeckers: all you have to do is look at the extent of their red caps.
Here is a page from my field notebook. I've recorded the band colors I was able to read on several woodpeckers. The circled numbers on the right side of the page are the individual bird ID numbers: by comparing the bands that I saw to a list of birds previously seen at this territory, I can usually confirm which birds I saw.
This particular census was special, though, because I found two birds at this territory that weren't there before. They are numbers 5700 and 5833. You'll see that I wrote a little four-letter abbreviation under each of those numbers: PLQE and PLAN, respectively. That means that those birds were listed as living on other territories (called as Plaque and Plaque Annex, or PLQE and PLAN), and they must have moved to this territory since the last time someone censused it. Finding out about birds that have moved like this is part of the reason we do these censuses. In a little while, the master list of the woodpeckers will be updated, and these birds will be transferred from their old territories to this group, called RE28.
2. Moving base stations
Natasha, the PhD student I'm working for, is specifically studying Acorn Woodpecker dispersal. Acorn Woodpecker "helpers" (young from previous years who stay on their natal territories to help raise the next year's chicks) spend some of their time scouting around for new territories that they might be able to move to in order to become breeders in their own right. Natasha has fitted a bunch of woodpeckers with solar powered nanotags, which are so light that the woodpeckers don't really pay any attention to them. The tags ping every so often as long as there is sunlight. To pick up the signals from the tags, Natasha has placed three base stations at various Acorn Woodpecker territories. The base stations have an antenna and a data logger. Every time the base stations get a signal from a nanotag, they record the date and time, which nanotag it was, and how strong the signal was. Natasha can use this information to figure out where the woodpeckers are going, when, for how long, and with which other woodpeckers (they often travel together with their broodmates).
The problem is, there are only three base stations (these things are expensive) and there are a lot of woodpecker territories. The base stations stay at each territory for two days, so every other day they need to be moved. Natasha has randomized the order of the territories that the stations go to.
Moving the base stations around like this gives Natasha a good sample of where the woodpeckers are spending their time. She hopes to use this information to figure out more about dispersal patterns: where are woodpeckers going, and why? They often disperse in family groups, but when do these groups form and how long do they last? I try to think about these big questions when I'm hauling a base station up a particularly steep hill.
3. Roost watches
Most of the woodpeckers on Hastings are color banded, but there are many that, for one reason or another, slipped through the clutches of the banders. If the birds aren't color-banded, we can't track their movements from group to group. And if there is more than one unbanded bird in a group, keeping track of the group's interactions becomes a nightmare.
Natasha plans to capture and band as many unbanded woodpeckers as possible. But capturing them isn't easy. To do that, she sets an ambush in the morning to catch them as they come out of their roosting cavity (Acorn Woodpeckers sleep in holes in trees, which helps keep them warm and safe from predators). The catch here is that there are a lot of holes in trees, and in order to catch the woodpeckers, Natasha has to know beforehand which cavity they're sleeping in.
Roost watches involve sitting very still for about 40 minutes right as the sun goes down and the woodpeckers go in to roost, watching the possible cavities and keeping track of how many birds go into which cavity.
4. Finding nests
It's breeding season for Acorn Woodpeckers! We have already found a few nests with eggs in them, and yesterday four chicks hatched in the nest of the woodpecker group that lives right by our house. Throughout the next two months, we will be monitoring the Acorn Woodpecker nests, banding the chicks, and doing feeding watches to determine which members of the group care for the babies, and to what extent.
When we census groups, we have to be on the lookout for possible nests. One indication is woodpeckers sitting in cavities during the daytime, sometimes sticking their heads out.
But hey, it's nice to have some variety.
My main work is with the woodpeckers, but I delight in watching the other birds and animals around here, too. The other day, I found an American Kestrel nest in a hole in a dead tree. One of my housemates is monitoring Western Bluebird boxes, and she has already found some babies.
On a few occasions, I've been bobcats walking around in the middle of the day. Mule deer roam the fields and there are apparently wild hogs around, although I haven't seen them yet.
On wet mornings, newts cross the road and cause delays.
Anna's hummingbirds zip around everywhere, showing off their beautiful pink throats.
And wherever you go, you can hear the "waka" calls of Acorn Woodpeckers. We'll see what the rest of the season holds. Here's to baby woodpeckers!
Jump to a Post
Welcome to Hawk Ridge
A Massive Migration
A Happy Birdthday
Photos from the Week
Visiting the Banding Station
A Watched Kettle Never Streams
Food, Part 1
The Big Picture
Last Weeks at the Ridge
Belize, Part 1
How to Look at Birds, A Guide (or: Belize, Part 2)
All Creatures Great and Small
Kids and Language, Again
More Photos from France
Food, Part 2
Building Nests in California
Please Do Not Pet the Woodpecker
Condors and Creatures in Big Sur
A Day at Hastings
I am a high school graduate taking a gap year before college. I’m interested in birds, biology, and the natural world, as well as history, foreign languages, writing, and reading.