Cold Feet

Herring Gulls in ice water

Looking at seabirds in winter raises comfort questions that we can scarcely relate to as thermally challenged humans.

Mallards on ice

How are these Mallards able to stand comfortably on ice? Why don't their feet freeze? Why don't they lose an unsupportable amount of body heat through their unfeathered legs? As a partial solution many birds at rest tuck one foot up against the warmth of their bodies, under the insulating feathers. They balancing on one leg, alternating the exposed and the protected one.

Robin on ice

The problem challenges any bird overwintering in this climate, whether standing or swimming.

Bufflehead

How do those legs keep functioning if they're super-chilled? This Bufflehead's foot, besides propelling the duck in powerful dives, dexterously satisfies an urgent itch.

Red-necked Grebe

Bird’s legs and feet are relatively free of soft tissue. The muscles that operate the foot are mostly located higher up in the leg and connected to the bones of the feet with long tendons. Because there isn’t much soft tissue in the lower legs and feet, there is less need for warm blood. Many birds also have valves in their leg arteries that control the blood flow, and there is evidence that some birds can pulse the blood to the foot. Every once in a while, warm blood flows to the foot to make sure it doesn’t suffer from frostbite.¹

Counter-current heat exchange ¹

Ducks, as well as many other birds, have a counter-current heat exchange system between the arteries and veins in their legs. Warm arterial blood flowing to the feet passes close to cold venous blood returning from the feet. The arterial blood warms up the venous blood, dropping in temperature as it does so. This means that the blood that flows through the feet is relatively cool. This keeps the feet supplied with just enough blood to provide tissues with food and oxygen, and just warm enough to avoid frostbite. Scientists who measured it calculated that Mallards lost only about 5% of their body heat through their feet at 0^o C (32^o F) . To put this in perspective, the rest of the duck is covered with feathers and in contact only with air, not ice, but because the body is relatively hot, 95% of the heat loss is from the head and body. ¹

Comfort is all in how you feel

A creature doesn't have to experience pain just because we do. If it's life systems are not in danger because of its adaptations, it is not uncomfortable.

Warm blood from the body going in the arteries to the duck’s feet is used to warm the blood coming back from the feet and into the body, in the veins. This has two advantages. First, it ensures blood going back into the body is warm. Second, it minimizes heat loss. The bird's toes do indeed get cold, several degrees colder than the body. But thanks to the counter-current exchange system, the body stays nice and warm. ²

Online sources:

1. T. C. Pelletier,  AskaNaturalist.com, April 22, 2010.
2. Chalisa Nestell, Phinizy Center for Water Sciences, 2014.

Sea Watch 2 - Seeing Pelagic Birds from Shore

A Conversation with Rick Heil

Rick's remarkable sighting report from Andrews Point, December 30, was featured in the last posting. Here he tells us about his approach to shoreline birding.

*  *  *

A promontory like Cape Ann that sticks out far into the ocean gets you closer to the pelagic birds that normally spend their lives far offshore. Sometimes you can see them from land, even during nice weather. It depends on the food that they're being attracted to that area, and also, of course, weather. Storms with strong easterly winds tend to push all these birds in from the fishing banks.

But I've had great days there when the weather is not unusual. Nice days.

You look for birds blown in from say Jeffrey's Ledge or Stellwagon Bank, all the way up the Gulf of Maine. They'll parade south offshore, like off Plum Island, off the coast of Maine. When they hit Cape Ann, because it juts out, they're forced to curl out around it. What they're doing once they're around the Cape, who knows. Going into Cape Cod Bay, maybe.

During major events like hurricanes all kinds of things can get blown far inland. These events are good for birders, but not so good for birds. Most of the birds survive these events. They are strong fliers. Or they just stop and rest. They'll find a sheltered spot in a cove or something, and ride it out. Sometimes on second or third days of nor'easters I've seen birds completely exhausted, just sitting on the water. At times like that, there's often heavy predation by especially Great black-backed gulls. I've seen them take Leach's storm petrels, dovekies, razorbills, all kinds of things. They swallow them whole. The victim tries to avoid them. It dives, or flies. A gull will hover, waiting for it to pop back up. Then it pounces right on it.

Peregrine falcons often take advantage of these storms too. I've see peregrines go offshore, fly around, hover, and pick off Wilson's Storm-Petrels. Storm-petrels are not here at this time of year. Wilson's Storm-Petrel might be seen any day during the summer, early summer especially. Leach's Storm-Petrels are mostly to occur in the fall.

Kittiwakes are fairly regular, close to shore. You can see them pretty consistently from Cape Ann, depending on the abundance of food in the area. Sometimes they'll even enter the mouths bays and river, like Newburyport and Gloucester Harbors. During a good blow they're very close by, just off the rocks. Others are a mile offshore. I try to count them from all these zones.

Besides skill, it's a matter of great optics. Superb optics. I can tell a Corey's from a Greater Shearwater probably at 2 to 3 miles. Holding the scope steady is very important. That's one of the main reasons why I do it from my car. I wedge my tripod in between my seat and my door, so it's rock solid. Then the wind is not really affecting me. Otherwise I have trouble seeing, because the wind is vibrating the scope and pushing me.

The only problem I have is when it's not easterly enough, and it's raining, I'm getting rain in the face and rain on the telescope lens. I know I'm missing things, because I'm constantly wiping myself. Also I wear glasses, so they're getting wet. Those are difficult conditions. I've always wanted to create something like a super lens hood. I tried one time and the wind blew it off.

I've sat there for ten hours, many times. I've done probably more than a thousand sea watches over the years since 1974. It's interesting from a scientific point of view, because things have changed over the years. Some species have declined, some species have increased dramatically. I still get surprises, even after forty-five years. Something that's unexpected, or numbers that are unexpected. Something that's out of season and unusual. Or a real vagrant, like an albatross, or a Black-capped petrel.

The distribution of seabirds really has more to do with food availability than anything else. In 2002 we had a huge incursion of juvenile herring into the southern Gulf of Maine. Tuna, dolphins, everything was going after them. We had a huge, huge seabird count that year. On September 28th I had 35,000 Greater shearwaters from Andrews Point. Later in October I had 839 Northern Fulmar one day, which was the high count that year. On October 12 I had 104 Puffins go by.

You can see these birds with a good scope, or if you want to sit out there during a nor'easter. The same birds that go by Andrews go by Halibut Point too. No difference at all.

Thanks, Rick!

Sea Watch 1

Early on the morning of December 30, six weeks ago, Rick Heil headed to Andrews Point next to Halibut Point knowing that conditions favored a good day for spotting offshore birds blown in to the coast. He stayed for eight hours with his tripod wedged between the car seat and the door, telescope protruding from the window. Here is his annotated report as posted on EBird, a website maintained by the Cornell Ornithological Laboratory. Where possible I include my own photos taken on less challenging days. But it's those strenuous conditions that brought in the phenomenal numbers of pelagic bird sightings.

Next week's posting will feature an interview with Rick on his seawatching experience.

Andrews Point, Rockport

December 30, 2019
8 hr, 10 min

Overcast, ENE winds 25-40 mph, sleet, snow squalls, and rain, with periods of no precipitation as well; 35˚F; visibility 3/4 to 3+ miles; seas 6-12 feet.

Excellent flight! This is what strong East winds can produce here compared to typically much less productive, but seemingly more frequent N-NNE or even NE winds. All birds moving NW to SE as usual.

12         Pomarine Jaeger

10         Dovekie - all singles

Dovekies

1,320    Common Murre

Common murres

Details: Epic! New all-time high count by a long shot! The largest single flock was eighty birds, but there were numerous flocks of ten to forty or more, some entirely comprised of this species, or mixed with Razorbills or with a Thick-billed Murre embedded. Most birds were in full winter plumage with extensive white high onto the face and behind the eye and with a thin black post-ocular stripe, although maybe 5% showed a partial hood / some duskiness on the face and throat but were clearly not Thick-billed Murres; all showed paler grayish-brown backs and upperwings (compared to blackish Razorbills), long, straight, sharp bills, trailing feet, and on close individuals, dusky streaks on the flanks.
Compare to previous high counts here: 438 on 16 Dec 2018, 420 on 12 Dec. 2002, 340 on 23 Jan. 2016, and 307 on 21 Dec. 2012. This certainly must also be an all-time high count for a species that's flagged as rare by Ebird!

16         Thick-billed Murre

Thick-billed murre

Details: Not an unusual count; All with mostly dark heads with paler throats; distinctive shape relative to Common Murre: more compact, much less sleek, almost neck-less in flight, with bill often pointed downward in flight; darker brownish-black upperparts, shorter thicker billed.

745       Razorbill - all in winter plumage

Razorbill

3           Black Guillemot

Black guillemot, winter plumage

1           Atlantic Puffin

Details: apparent juvenile: small squat alcid, larger than Dovekie, all dark underwings, dusky face, broad bill but less than adult

2,730    Black-legged Kittiwake

Black-legged kittiwake

Kittiwakes, juvenile (L) and adult (R)

Details: counted;  approximately 2635 adults, 95 - 1W; third-highest all-time count here for me: cf., 4300 on 3 Nov. 1999, 4260 on 21 Oct. 1996, and 2425 on 9 Dec. 2009.

1           Northern Fulmar

Alcids and Evolution

Razorbills

Day before yesterday the Brookline Bird Club sponsored a tour around the Cape Ann coastline hoping to spot alcids, seabirds that normally winter offshore diving for food in nutrient-rich waters above the Continental Shelf. If you're lucky and persistent you may see individual alcids near shore. More often they're specks hurrying by half a mile out, glistening white bellies contrasting with rapidly beating black wings.

Razorbill

Razorbills are the commonest alcids that might be glimpsed at Halibut Point, mostly beyond crisp camera range. They have distinctive silhouettes, heads tilted back and upward like a loon, large bills dominating their foreheads.

Dovekie

Pigeon-sized Dovekies are the smallest of local alcids. Their short broadly conical bills are adapted to catching tiny crustaceans underwater. A Wikipedia article notes they may require 60,000 of these a day to support themselves in the North Atlantic. Like the other alcids, they only come to land during nesting season.

Dovekies were the advertised prize goal for the Brookline Club tour. For many in the group it would be a Life Bird, meaning their first authenticated sighting if they had a lucky day.

Black guillemot, fall-winter plumage

A more likely observation from shore is the Black guillemot, which may be seen here at this season either in its high-contrast breeding plumage or in the whitish eclipse plumage it takes on in late summer and fall.

Black guillemot, breeding plumage

Guillemots are more adapted to fishing near shore than the other highly pelagic alcids.

Thick-billed murre and Common eider

Strong-swimming murres that pursue fish show a very different bill structure than a duck that pulls its food from the ocean bottom. Alcids are restricted to cooler northern waters because pursuit diving becomes less efficient in warmer waters. The speed at which small fish can swim doubles as the temperature increases from 41 to 59 °F, with no corresponding increase in speed for the bird.

Common murre

In our area Common murres may be the least common of the alcids that may reasonably be seen here, excepting the even rarer Atlantic puffin.

In the region where alcids live, their principal seabird competition are cormorants (which are dive-powered by their strong feet). In areas where the two groups feed on the same prey, the alcids tend to feed further offshore.

You will have noticed similarities in appearance between alcids and penguins. This carries over to their strong swimming ability and the use of their wings to gain speed and agility underwater. Both groups stand with an upright posture on land because their legs are located relatively far to the rear for best diving propulsion.

Although not to the extent of penguins, alcids have largely sacrificed flight, and also mobility on land, in exchange for swimming ability; their wings are a compromise between the best possible design for diving and the bare minimum needed for flying. [Much of the foregoing is from Wikipedia.]

Examples of Convergent Evolution:

(1) Dovekie's resemblance to (2) Diving petrel

(3) Razorbill's resemblance to (4) Magellanic penguin

Chris Leahy, The Birdwatcher's Companion

It would be easy to suppose that alcids and penguins are linked by common ancestors. However genetic analyses have demonstrated that their similarities have developed from independent like responses to similar ecological circumstances. Very different ancestors evolved to specialize on the same feeding opportunities to produce look-alike species in a process known as adaptive convergence.

Local resident Chris Leahy presents authoritative and alluring information such as this in his encyclopedic Birdwatcher's Companion (2004).

For the book's cover illustration he has chosen a pair of nesting Tufted puffins, Pacific relative of the Atlantic Puffin alcid I have yet to see at Halibut Point. One of these nor'easters I may squint into the winds, sleet, and frigid temperatures that drive pelagic birds toward shore in hopes of that first sighting. So far I've excused myself for the sake of my camera. Chris says that "in flight off Halibut in winter plumage they are easily overlooked: small, dull (no big colorful bill sheath) flying fast close to the water." And probably half way to the horizon. Happy birding to you!