For some reason, the barn swallows at the marine lab like building their nests above doors. It seems that little 1/2-inch ledge of the door frame provides support for the mud nest. And the birds don't always choose little-used doors, either. This year a pair constructed their nest above one side of a double-door that people walk through all day. The mother laid and incubated her eggs, but would occasionally get flushed off the nest if someone came through the door. I always tried not to disturb her any more than necessary. The animal is always right, so I figured she knew what she was doing.
The eggs hatched about a week ago, I think. The mom would sometimes leave the nest when people approached, and even though I couldn't see anything in the nest I'd hear little cheeps. Earlier this week I thought I could see little heads poking above the edge of the nest.
It seems there are three baby birds in this nest!
I haven't spent much time watching the nest closely, because I don't want to scare the mother off and keep her away. Today I was lucky and stuck around just long enough, and with the big camera at hand, to capture both parents returning to feed the babies. The first parent arrived with an insect and landed on the nest. The other parent alit on the door frame.
After depositing the insect into one of the gaping yellow mouths, the first parent flies off. The second parent doesn't seem to have anything to offer the babies, though.
Ooh, maybe this parent has food!
The second parent lands on the nest. . .
. . . and promptly takes off again. . .
. . . leaving the babies alone in the nest again.
These babies still need to grow feathers, although they are clearly big enough to thermoregulate without a parent sitting on them. Growing feathers takes a lot of metabolic energy, and aside from when the parents arrive with food the nestlings will sleep. But it's funny. They seem able to keep an eye (or maybe an ear) out for the parents flying around, and whenever one flies past the doorway they all perk up and start cheeping. There are lots of swallows at the marine lab right now, and I wonder if these babies can identify their parents from among all the other adults in flight.
They'll grow fast, being fed frequently by their parents. They'll have to get big and strong, to prepare for their migratory trip south in the fall I've never noticed exactly when they leave, I think because by the time they head south they've dispersed from the nest site. I always look forward to their return in the spring, though.
Every year we are fortunate to watch a pair of red-tailed hawks (Buteo jamaicensis) raise young in a tree across the canyon. We're not always sure if the parents are the same birds every year, and I think this year's female is a different bird from last year. Her mate may be the male who has used this nest site for a couple of years now, but again, we don't know.
This year the parents raised three youngsters, who have just begun leaving the nest. They prepare for their first flights by making their way to the edge of the nest and flapping their wings to exercise the flight muscles. This is usually fun to watch, as they don't seem to care whether or not a sibling is in the vicinity. This flapping activity begins before the bird is fully feathered, and they look like awkward punk-rocker teenagers, trying to be cool and not even close to pulling it off.
The hawk nest is in a eucalyptus tree. As the time to fledge approaches, one or both of the parents often perches at the top of a nearby cypress tree. Usually the youngsters' first flights are to the cypress tree. Cypress trees may be the ideal location for fledging, because they have lots of soft-ish branches to fall on when the birds biff the landing. The first flights don't go far from the nest, and the birds end up hopping along branches as they flap their wings. So they are called branchers.
With raptors, the females are bigger. Males tend to leave the nest before their sisters, who have more growing to do, so we always assume that the first one to depart is a boy. This year the females lagged by only a day or so behind their brother. And all three of them seem to be progressing pretty quickly, compared to cohorts we've watched in previous years. Good little branchers!
We watched these two for a while in the early evening. I don't know where the third one was. The branchers watch their parents soar around effortlessly. Here they are at the very top of the cypress tree:
Okay, my digiscoping skills need work. I did, however, get lucky enough with the spotting scope and my phone to catch a few video clips.
You can see them trying to maintain their footing as the wind blows the tree around. They're able to use their wings for balance, but then they catch a little lift and get knocked about. In the second clip one of the birds is hanging out when its sibling crashes into it. If they were human teenagers, you'd hear one yelling "Look out below!" while the other hollers "Get off me!" Yeah, landing is toughest part of flight!
Over the next few weeks the branchers will get better and better at landing, and their flights will get longer. They will learn how to find thermals and soar. Their parents will continue to provide food for them, but at some point the kids will learn how to hunt on their own. Rodents of the neighborhood, look out! Eventually the branchers will be as badass as their parents. Then they'll disperse to find territories of their own.
We have all heard about hummingbirds and their ability to hover and fly backwards. These tiny feathered jewels are a delight to observe. They are birds of the New World, and I feel sorry for people living in parts of the world that don't have hummingbirds. Where I live, on the coast of Northern California, the resident hummers are Anna's hummingbirds (Calypte anna). We get the occasional Rufous and Allen's hummers (Selasphorus rufus and S. sasin, respectively) passing through on their migrations, but the Anna's are here year-round. We have front-row seats to watch their mating displays, and I know they must be nesting nearby even though I've never managed to locate a nest.
The other day, while sheltering in place at home, I went outside to photograph birds. The Anna's hummers were putting on quite a show. The males have been displaying since February, flying straight up-up-up and then plunging into a J-shaped dive near an observant female. At the bottom of the dive the male uses his tail feathers to create a sharp and very loud chirp. When this occurs about a meter from your head, it sounds like a pistol shot. Trust me on this.
Anyhow, that day I was lucky and captured some shots of a male Anna's hummingbird hovering in place. These aren't National Geographic quality photos, but then again I'm not a National Geographic-caliber photographer. For anyone who is interested in such details, here are the EXIF data:
300mm f/4 lens
1/2500 sec at f/4
At a shutter speed of 1/2500 sec, you can freeze even the movement of a hummingbird's wings. You can see very clearly that although the bird's wings are moving, his head remains perfectly skill and his position doesn't change at all.
A hovering hummingbird moves its wings in a figure-8, similar to the sculling motion of a skilled rower. If you use your imagination a bit you can see the rotation of the wings in this set of photos.
Given the mandate to shelter in place at home, I don't know how many of the upcoming morning low tides I'll be able to explore. On the one hand, I'd be by myself, not risking exposing anyone to any germs I might be carrying. On the other hand, staying home means, well, staying home. The tidepools are calling to me, but this year I might not be allowed to accept the invitation. All for the greater good, right?
We Californians are all under a state-wide mandate to stay at home, to minimize the spread of COVID-19 this spring. School hasn't been cancelled, but all classes have converted to distance learning. I had four days to figure out how to deal with that. Fortunately we are in spring break this week, which gives us all a little bit of a breather. I'm going to use the time to catch up on grading and plan for the second half of the semester.
The marine lab is also closed for business. Only essential personnel are allowed to be there. The term 'essential personnel' includes people whose responsibilities are animal husbandry. Since animals will die if I'm not there to feed them, I have met that criterion for essentiality. That's not a word, but you know what I mean. With so many fewer than usual people at the marine lab, there's a lot more wildlife activity. A few days ago I saw a long-tailed weasel (Mustela frenata) chase down and capture a young brush rabbit. I just barely had time to catch a quick shot with my phone.
The most noticeable thing, though, is the increased birdsong. The sparrows, finches, red-winged blackbirds, mallards, doves, towhees, and hawks are all making a lot of noise. The barn swallows (Hirundo rustica) returned to the lab on the 21st, right on time! Maybe this year they'll have a more successful nesting season than they did last year.
Yesterday I witnessed something I'd never seen before: a territorial dispute between a black phoebe (Sayornis nigricans) and a barn swallow. The fact that I had never seen it before in no way implies that it happens only rarely; maybe I've just never paid that much attention to these things before, or they've never happened while I've been around to watch.
Here's the story, in a series of snapshots.
Prologue. The barn swallow (H. rustica) is perched on one of the outdoor light fixtures. The phoebe (S. nigricans) swoops up from below.
The swallow takes to the air, only to be divebombed by the phoebe.
The swallow retreats. . .
. . . and the phoebe perches, triumphant, on the rain gutter.
The entire altercation lasted maybe as long as four seconds. I didn't see where the swallow flew. The phoebe remained on the rain gutter for about a minute or so, then took off over the meadow. Perhaps it has a nest somewhere nearby and was defending it. Both species build mud nests on cliffs and buildings, so these birds could be competing for nest sites. Or maybe phoebes just don't like swallows. Either way, this was the sort of interaction that I don't notice when there is a lot more human activity at the marine lab. Nature has a way of re-asserting herself when humans are removed from the scene for even a short period of time.
It's no secret that I love pelicans. I love watching them soar low over the waves, where they are truly in their element. I love watching them plunge from the air into the water and then bob right back to the surface, because unlike their cormorant relatives, pelicans can't fly underwater. And I love watching them plunk around on land, where they are dumpy and awkward but still somehow elegant.
The other day I ventured out between storms to photograph birds. As per usual I ended up down at Natural Bridges, where pelicans were hanging out on the last remaining rock arch. They were well within the reach of my long lens, so I took a lot of photos.
The best photos I got were of a subadult pelican coming in for a landing.
Landing gear down!
Decreasing air speed:
And. . . touchdown!
A job well done!
The youngster managed a safe landing without knocking one of its compadres into the water. That isn't always the case--those wings can do a lot of damage. But the three adult birds on the left hardly seemed to notice, which means the youngster has learned how to stick the landing without disturbing everyone else in the vicinity. I'm sure that's a lot easier said than done!
Autumn is migration season in California. We all know that, in the northern hemisphere, birds fly south for the winter and return north for the summer. And indeed, this is a very good time to go bird watching along the Pacific Flyway, as migrating birds stop to rest and feed at places such as Elkhorn Slough. Here in Santa Cruz, autumn is punctuated by the return of monarch butterflies (Danaus plexippus), roosting in eucalyptus trees at Natural Bridges State Beach and Lighthouse Field.
Since 1997 the Xerces Society for Invertebrate Conservation has been tracking monarch sightings on their migrations between the western U.S. and Mexico. They conduct a volunteer butterfly count every Thanksgiving. More recently, community science data sources such as iNaturalist provide much of the information.
This morning, before it got warm, I went to Natural Bridges to see how the monarchs were doing. I wanted to photograph clumps of butterflies dripping from tree branches. It seemed, however, that there aren't as many butterflies as I remember from previous years. The clusters were not nearly as large or as dense as they should be. And the data shown in the figure below do demonstrate a precipitous decline in monarch since 2017. We're still a couple of weeks away from this year's Thanksgiving count, and there is still a chance that the butterflies might arrive in larger numbers.
Trained observers know how to estimate the number of butterflies in a cluster like this. The numbers of butterflies at various roosting sites are aggregated to assess overall population sizes.
This morning I did see one butterfly that had a tagged wing. It was wearing a green Avery round sticker, with some writing in what looks like black Sharpie. The color of the sticker was very close to the green of the surrounding foliage, so I wasn't even able to see the sticker until I downloaded the pictures from the camera.
At first I thought the tag resulted from an official scientific project or undertaking, but it turns out that anyone can tag a monarch. The tags are used to track migration of the butterflies. There doesn't seem to be a central depository of tags and their origins, so knowing the color of the tag doesn't tell me where this particular butterfly came from.
Once the sun hits the butterflies and they begin to warm up, the clusters start breaking apart. Butterflies open and close their wings, exposing the darker dorsal surfaces to the sun and warming up their flight muscles. Sometimes they dislodge one another.
On a cool morning like this, many of the butterflies that fell out of the clump couldn't fly yet, and landed on the ground. The boardwalk is perhaps not the safest place for a butterfly to wind up, but at least in a monarch sanctuary such as Natural Bridges the visitors are knowledgeable and look out for the butterflies' safety.
As I wrote before, the butterflies we see at Natural Bridges this year were not born here. This means that their survival to this point has depended on healthy conditions in the Pacific Northwest and the western slopes of the Rocky Mountains, where they lived as caterpillars and emerged from their chrysalises. This also means that planting milkweed for monarch caterpillars in California won't help the butterflies that we see here, although it would help butterflies that are destined to overwinter elsewhere. What will help local butterflies--monarchs and otherwise, and all nectar-feeding insects, in fact--is planting California native plants, to provide them with the nutrition they have evolved to survive on.
People call them air rats or trash birds, but I really like gulls. Especially the western gull (Larus occidentalis), known colloquially among birders as the WEGU. Yes, gulls eat garbage, but that's only because humans are so good at making garbage and leaving it all over the place. Other gulls may travel quite far inland--in fact, the state bird of Utah is the California gull (Larus californicus)--but the WEGU is a California Current endemic species. This means that its natural food sources are the fishes and invertebrates of the California Current, which flows southwards along the west coast of North America. As a result, it lives in only a very narrow strip of coastline, nesting on cliffs and restaurant roofs.
Case in point. Yesterday afternoon I was at Moss Landing with my marine biology students. We had hiked along the road, over the dune to the beach, down the beach a ways, and returned over the dune to circle back to our starting point. The last item of note that we all watched was a western gull hunting along the shoreline of the Moss Landing harbor.
It had grabbed a crab. It looked like a rock crab, but I couldn't tell what species.
The crab wasn't dead, and was thrashing around enough to make it difficult for the gull to get a good grip on it.
The crab gets a reprieve!
But the gull didn't give up. It reached down, came back with the crab in its beak, and then flew off.
Over the holiday weekend I was in Morro Bay for a surprise 80th birthday party--not mine! The party on Friday evening was a huge success (none of the guests let the cat out of the bag), the birthday girl was completely taken by surprise, and a good time was had by all. The weather was cold and sporadically stormy the entire weekend, but the clear spells between storm squalls were gorgeous and almost a little warm.
Since it wasn't raining on Saturday morning, we went out to Morro Rock to look for peregrine falcons. There are two (I think) pairs of falcons nesting on the Rock, one of which nests on the side of the rock that is visible to people. This is nesting season, and Morro Rock has a lot of ledges that make good nesting platforms. Peregrines don't make a nest, really. They lay eggs and incubate them on ledge high up on structures--rock cliffs, buildings, bridges--that dominate the landscape. We did see one peregrine way up on the rock, identifiable through binoculars but far enough away that I couldn't get a decent photo. This is the best I could do:
So not much success with the falcons, although I could at least document that they were there. Turning away from the Rock I was able to watch a great blue heron (Ardea herodias) go after and catch and eat a juvenile rockfish! The photos tell the story, so I'll just post them.
And finally, down the hatch it goes:
And there you have it! On a day when it was too blustery for human fishers to venture out of the bay, one avian predator had a successful morning. Way to go, bird!
People who moved here from other states often say that California doesn't really have seasons. I think what they mean is that in general we don't oscillate between frigid winters and hot, humid summers. The Pacific Ocean moderates weather conditions through most of the state, giving us our Mediterranean climate characterized by a short rainy season and a long dry summer. However, California is a very large state with many different climate zones. Here on the coast our summers are cool and foggy, while in the interior of the state summers can be quite hot, upwards of 38° C for weeks at a time. Snow falls in the Sierra Nevada, providing much of the state's annual water budget, but the rest of the state usually remains snow-free for most of the winter.
That said, California does of course have seasons, even though they may not be as in-your-face as what you'd see in, say, New England. One of the ways to experience the seasons is to observe the comings and goings of migratory wildlife, especially birds. In fact, bird migration patterns make up a significant part of phenology, the study of the timing of biological events in the natural world. California's position along the Pacific Flyway provides fantastic bird watching opportunities throughout the year. There are many locations within California that are pit stops for birds migrating up and down the coast and overwintering oases for birds that breed much farther north.
The San Luis National Wildlife Refuge (NWR) in Merced County is one such place. Located in the Central Valley, it represents some of the original habitat in this part of the state. The San Joaquin River winds through the Reserve, providing riparian habitat, although the river is currently a mere ghost of its former glory. Since 2009, federal and state entities have worked to restore the San Joaquin, increasing water flows and cleaning up the surrounding lands. While it would be marvelous to see chinook salmon once again migrating from San Francisco Bay up the San Joaquin, it hasn't happened yet. The re-establishment of salmon runs up to just below Friant Dam would indicate a healthy San Joaquin River, and I really hope to see it in my lifetime.
Before the era of modern agriculture, much of the Central Valley flooded with the winter rains and spring snowmelt. Only a tiny fraction of these wetlands remain; most have been drained for agriculture and further deprived of water by state and federal water diversion projects. In areas such as these, small pools form during the wet season. These vernal pools--so called because they are often at their deepest during the spring--are ephemeral habitats. They almost always disappear during the long dry summer, but during their short existence they provide living space for a unique biota. A few vernal pools occur in most of the flat areas of California, although there are far fewer of them than before, and they differ biologically throughout the state. It is not uncommon for each vernal pool in a given area to have its own combination of flora and fauna, all of which have adapted to thrive in both desiccated and flooded conditions.
On our way back to the coast after spending Christmas with my family, we stopped at the San Luis NWR to do some wildlife watching. The visitor center was closed because of the federal government shutdown, but the roads were open. The Refuge has two auto tour routes, one to the tule elk reserve and the other to see resident and visiting aquatic birds. We chose to drive the bird route, because winter is a good time to see birds that spend the rest of the year at much higher latitudes.
Coots (Fulica americana) are ubiquitous in California's wetland habitats, and because of that they are easily overlooked. When I was little we called them 'mudhens' and smirked at them because they weren't ducks. Of course I now realize that that thinking is entirely unfair, and have come to appreciate coots because they aren't ducks.
In addition to the coots, which weren't much of a surprise because we expected to see them, we saw large numbers of several species that we weren't as familiar with. There were ducks and geese, which took us some time to ID because they weren't mallards and Canada geese. Fortunately I keep a bird field guide and binoculars in the car! My favorite bird ID book is the National Geographic Field Guide to the Birds of North America; we keep one of the later editions at home, but my beloved and well battered third edition lives in the glove compartment.
The ducks turned out to be northern shovelers, which I've seen at Elkhorn Slough. True to the typical avian way of doing things, the males are strikingly colored, with brilliant green heads, while the females are a dark streaky brown. In the photo below, a female swims with two males.
The geese were entirely new to us. We first saw them flying overhead in the V-shaped formations that you expect from a gaggle of geese in the air. But they didn't honk like Canada geese so we knew right away that they were something different.
I wasn't able to ID these until we got home and I looked at my photos on the computer. iNaturalist helpfully gave me a tentative ID of greater white-fronted goose (Anser albifrons), which I was happy to go along with.
In North America, greater white-fronted geese nest in the Arctic of western Canada and through most of Alaska, including out along the Aleutians. They migrate south to spend the winter along the Gulf coast and along the eastern coast of the Sea of Cortez. The winter wetlands of the Sacramento and San Joaquin Valleys host many of these geese, and smaller numbers overwinter in coastal Oregon and Washington.
Living in California, I don't usually expect to encounter any species whose common name includes the word 'tundra', but tundra swans do indeed spend their winters here! They nest in the very high Arctic on tundra, a habitat that is threatened by climate change, and winter is the only time we would see them in the lower 48, when large flocks venture south to overwinter near lakes and estuaries. I'll keep an eye out for them next time I'm at Elkhorn Slough or Moss Landing.
We saw hundreds of these swans hanging out with the shovelers. Only a few were within photograph range, as I don't have a very long telephoto lens (yet!), but there were lots of large white blobs floating, foraging, preening, and sleeping. They were fun to watch through the binoculars. We had hoped to see some sandhill cranes in the Refuge, too. We had seen them off in the distance, much too far to be photographed, but it wasn't until we were on the last leg of the auto tour that we saw them up close. They were not mingling with the swans and geese, and as far as we could tell tended to gather in single-species flocks. They seemed to be more skittish, too, and would startle and fly away when they heard human noises. I had to move slowly and quietly to get this close to them. Even the sound of the camera shutter caught their attention and made them wary.
The Central Valley is Ground Zero for sandhill cranes in California, where they can be seen only in the winter. They don't breed here, of course, but there is a small population of ~460 pairs of sandhill cranes breeding in far northeastern California. There are locations in the Central Valley that are known for hosting large crane populations in the winter, and one of my goals is to witness a big 'fly-in' event, when huge flocks come in to roost in the evening. I've seen pictures, and it looks like a spectacular sight. I want to see it with my own eyes.
All this is to say that we do indeed have seasons in California. The shifts between summer and winter are perhaps more subtle here than in other states, but an observant eye keeps track of changes in the natural world. And you don't have to be a trained scientist to track seasonal changes wherever you live, either. We tend to use temperature to tell us which season we're in, but in reality light is a much more reliable indicator. Just think of how dramatically temperature can fluctuate in a few days, and how much more extreme these fluctuations seem to be in recent years, due to climate change. Day length cycles, however, remain constant over geologic time, as we humans haven't yet figured out a way to mess with the tilt of the earth's axis. Everyone notices how the amount and quality of light change with the seasons. It takes just a little more effort to notice the ways that life responds to those changes.
A few years ago I had a student, Brett, who had played baseball while he was in high school. One day in lab the students and I were chatting about nothing in particular when the conversation turned to the difficulty of memorizing the scientific names of all the animals they were studying. We got into one of those debates about the usefulness of common names as opposed to scientific names, and I got on my soapbox to deliver my usual sermon: common names are fine, if you are talking with non-scientists and as long as the names are unambiguous, but for scientific communication and to avoid confusion and ambiguity you need to use an organism's scientific name. Also, taxa that have been well studied for decades or centuries, such as birds and flowers, often have common names that are widely accepted and used by both scientists and naturalists. This evolved into a discussion of bird-watching and how birders have developed a sort of shorthand for birds' common names; RTHA for red-tailed hawk (Buteo jamaicensis), for example.
At this point Brett chimed in with a bit of wisdom imparted by one of his high school baseball coaches, who said, "All you need to know to identify birds is whether or not it has webbed feet. If it has webbed feet, it's a duck! And if it doesn't have webbed feet, it's a pigeon!" I must say, as far as methods for distinguishing different groups of birds, I have heard worse. The possession of webbed feet at least has a functional significance, and it's usually easy enough to see a bird's feet, or at least to infer the presence or absence of webbing by observing the bird in its habitat.
My own proficiency at IDing birds is sketchy at best. I'm pretty good with the birds that I see all the time in my backyard and canyon, and I can get most other sightings down to major group, but there are some types that I will probably always find difficult. Gulls and the wading shorebirds, for example. Gulls are notoriously problematic because there are many species and they go through three or four juvenile stages before attaining adult plumage. Wading shorebirds (sanderlings, and whatnot) all look alike to me, and absolute size differences are hard to discern when dozens or hundreds of birds running up and down the beach are about the same size.
One bird that I can easily identify based on its silhouette, is a cormorant. They are related to pelicans and have the same gular pouch under the throat that they use to catch fish, but are their bodies are much more streamlined. Unlike pelicans, which dive from the air to catch fish, cormorants are pursuit divers, using their webbed feet to swim after fish below the surface. These webbed feet are located at the posterior end of the body, where they are well positioned for propulsion under water (think about where a submarine's propeller is located). Having their feet at the back end of the body gives cormorants a more upright stance on land compared to pelicans, whose feet are positioned towards the middle of the body and thus carry themselves along a more horizontal axis.
Clearly, despite their webbed feet, cormorants are not ducks. However, like ducks they do spend most of their time on or in the water. Cormorants are unusual for aquatic birds in that they don't have oil in their feathers. You've heard the phrase "Like water off a duck's back", right? It means not being affected by external events, instead letting them roll off and away the way that water beads and falls off a duck's plumage. The saying is true because ducks and other waterfowl do indeed have a coat of oil in their feathers. In fact, most birds have feathers that are water-repellent to some degree. The oil keeps water from penetrating through the feathers and chilling the body. It also provides additional buoyancy. When you see a bird preening, part of what it is doing is distributing the oils over the feathers in an even coat.
Not having oiled feathers, cormorants soon become waterlogged, which enables them to stay underwater and swim efficiently below the surface. Unfortunately, getting soaked to the skin means the cormorants are susceptible to hypothermia. When they have finished feeding, they need prepare their feathers before they can make any prolonged flights. You will often see cormorants perched on rocks or cliff ledges, basking with their backs to the sun and wings outstretched. They have to do this to dry their wings and warm up their bodies before they can fly. Their dark coloration absorbs heat quickly and speeds up the drying process.
Even though they don't have oiled feathers, cormorants do spend a lot of time preening. They use their beak to smooth feathers and make sure they lie properly on the body. Usually they pay special attention to the wing feathers, as the proper condition and alignment of these feathers makes flight possible.
Another characteristic that makes cormorants different from ducks is their solid bones. Almost all of the flying birds have hollow bones, to lighten the load they have to carry through the air. Flight is a very energetically expensive endeavor, and over millennia the hollow skeleton has evolved to make it slightly less so. Penguins, of course, do not fly in air, but their swimming motion is essentially underwater flight. They have solid bones, to provide weight and counteract the positive buoyancy generated by their blubber and oiled feathers. Like their flightless tuxedo-wearing relatives, cormorants also have solid bones, to help keep them underwater as they pursue fish.
The hitch in this plan for cormorants, however, is that they do fly. Cormorants travel through the air and hunt for prey in cold water. They certainly aren't the only birds with this combination of habits; there are tern species, for example, that migrate thousands of miles and feed by plunge diving. But cormorants, being pursuit divers, spend more time underwater than most other flying birds. They have had to evolve a combination of adaptations for flight (flight feathers, wings long enough to enable flying) and adaptations for swimming underwater (legs at the back of the body, lack of oil in feathers, and dense bones). Natural selection is often about just this sort of compromise. An organism doesn't have to be perfect to be fit for its environment, but it does have to be good enough. And when an animal spends time in both air and water, it has to be good enough in two environments. Cormorants, traveling through air and hunting in water, manage to be successful at both and thus persist.