Alaska Birding with PIB: Anchorage to Seward 18 June 2019

Red crossbills (Loxia curvirostra) are conifer specialists that breed across North America and Eurasia, from Alaska to Newfoundland, from Scotland to Japan. They are so tied to spruces, pines and firs that you won’t find them in deciduous forests nor anywhere that the cone crop has failed. That explains why in three decades I’ve seen only one red crossbill in western Pennsylvania.

Red crossbills eat conifer seeds by prying open the cones using their crossed bills. Their beaks have evolved to match the cones they open — and so have the cones. A 2010 study led by C. Benkman showed that it’s a continuous arms race in which the cones evolve to foil the beaks and the beaks evolve to open the cones. The crossbill-cone competition has resulted in 21 subspecies of red crossbills with different beaks and call types. One population in Idaho, the Cassia crossbill (Loxia sinesciuris), was given separate species status in 2017.

Crossbill beaks are such important tools that a bird’s right-handedness or left-handedness is expressed in the crossing of his beak. Individual beaks cross right or left, as shown in the two male crossbills above.

Though red crossbills don’t migrate, they range far and wide in search of food, calling “jip jip” as they fly. Their flocks are usually noisy but fall silent when they’re feeding intensely. In his Essential Field Guide Companion Pete Dunne describes them as Eclectic Parrot-Finches: wide-ranging, social, and parrot-like in behavior.

Red crossbills favor old growth conifer forests because the cone crop is heavier on trees more than 60 years old. If I’m lucky, today I’ll see the “Red Parrot-Finch of the Pines” near Seward, Alaska.

UPDATE: I wasn’t lucky. 🙁

(photo and base map from Wikimedia Commons, breeding range drawn freestyle by Kate St. John; click on the captions to see the originals)

Alaska Birding with PIB: At Tangle River on Denali Highway 17 June 2019

In western Pennsylvania we rarely see longspurs, the sparrow-like birds whose long hind toe gives them their name, but two species of longspurs breed in Alaska.

Lapland longspurs (Calcarius lapponicus) are the most conspicuous songbird on the tundra as they prominently claim territory and a mate. The males flutter and sing above their chosen patch, advertising themselves in loud flight song displays.

Smith’s longspurs (Calcarius pictus) are harder to find partly because of their lifestyle. They don’t claim a territory, they don’t claim one mate, and they don’t use flight song displays. Instead the males sing from the top of a twig, “Hey, ladies! Come here.”

When a female shows up the two go through their courtship displays and copulate. Then they both go off to mate with other birds.

The fancy name for this is polygynandry. Each female and each male pairs and mates with two or three of the opposite sex. These birds are very busy during the breeding season!

Over a period of one week in the early spring, a female longspur will copulate over 350 times on average; this is one of the highest copulation rates of any bird. Males are well-equipped to deliver such large numbers of ejaculates—their testes are about double the mass of those of the monogamous and congeneric Lapland Longspur.

Birds of North America, Smith’s longspur account

Every nest contains chicks of mixed parentage — the same mother, various dads. Fathers choose a couple of females and try to insure that most of the chicks are their own.

Males do not defend territories, but instead guard [their] females by following them closely. [Males] compete for fertilizations by copulating frequently in order to dilute or displace sperm from other males.

Birds of North America, Smith’s longspur account

When John James Audubon named Smith’s longspur for his friend Gideon B. Smith he was unaware that these birds had such an unusual social life. It took a long time for humans to figure it out, beginning with pioneering behavioral work in the 1960s and now DNA tests today.

Inside the calm exterior of a Smith’s longspur is a very promiscuous bird.