Saturday, April 11, 2015

Magpie Behaviors

Black-billed Magpie carrying nesting material (c) John Ashley
Black-billed Magpie (probably a male) carrying nesting material

Growing up the youngest of seven sons, I was always half as big and half as strong as my older brothers. So I adapted by spending a lot of time alone in the woods, somehow surviving to fledge into an adult-sized, curious biologist. This probably explains why I always pull for the underdog. Or in this case, the "underbird."

Magpies have a bad rap, even among birders, because they're raucous and they sometimes eat the eggs and chicks of other birds. But I've consumed more birds and eggs during the past year than any magpie has managed in a lifetime. They don't judge me for surviving on Costco's broiled chickens, so I don't judge them.

All of Europe and much of Asia is home to one or more of the 13 magpie subspecies. In North America, the Black-billed Magpie (Pica hudsonia) is strictly a bird of western U.S. and Canada. Humor me for a few minutes by keeping an open mind while I offer a few reasons why our Montana magpies should be mentioned whenever we talk about our most interesting native birds. Actually, we have a lot of behaviors in common.

Right off the bat, magpies are undeniably smart. They cache food for later use, and they vary the distribution of their caches depending on how many other magpies are in the area - more magpies present causes individual birds to protect their caches by spacing them farther apart. Magpies also recognize themselves in a mirror and seem to understand the concept of self, a complex cognitive ability that we like to reserve for "higher" animals. In addition to magpies, self-recognition has been demonstrated only in elephants, dolphins and apes (including most people). It suggests that the magpie's corvid cousins, the crows and ravens, might also posses this ability.

Magpies also proclaim a "cheeky" behavior around their hawk, owl and human predators. They sometimes approach, land nearby and sing to their enemies. This reminds me of a melodious version of the old warring Scots who, before battle, would lift their kilts to moon their enemies. It's hard to say for sure, but we suspect that this magpie behavior is used to gain status within a non-breeding flock or within a group of nesting adults, another way of proving one's fitness - if one survives.

And this brings us to another interesting behavior that I've yet to witness, but it has been documented by other people many times - the magpie "funeral." When a magpie discovers a fallen comrade, he calls loudly to attract other magpies, and a noisy group gathers around the deceased. After 10-15 raucous minutes, the entire flock of "mourners" suddenly flies away in silence.

Meanwhile, a magpie myth was recently proven false. One of the definitions for magpie in the Collins English Dictionary is, "a person who hoards small objects." But a 2014 study published in Animal Cognition actually showed the opposite for our avian magpies. In a controlled experiment, magpies avoided unfamiliar, shiny objects like rings and tin foil. They even avoided tasty nuts that were placed close to the shiny objects. Magpies are not the compulsive thieves of human legend.

Our native magpies are honestly handsome when viewed without preconceived notions. Their glossy and bold, black and white suit underlies the subtle beauty of iridescent feathers that appear blueish-greenish-purplish-black, depending on the viewing angle. (Iridescence involves refraction inside the feather and reflection from inner and outer feather surfaces.) Add in the longest tail of any corvid - half of the magpie's body length (9"-12", 23-30 cm) is tail feathers - and these birds present a compelling if not comical package, sort of like a prom night senior strutting about in his rented tuxedo.

Partly due to that long tail, magpies can't out-fly their enemies, but they can out-maneuver them. Magpie territories almost always contain edge habitat where grassy foraging areas mix with tree or brush cover. When pursued by a hawk or owl, a magpie flies in among thick tangles of branches where the larger bird can't follow.

Magpies also deter predators by building their large nests out of thorny sticks and small branches. Nest construction lasts 3-6 weeks and culminates in a complex structure 2-4 feet (1 m) wide. Magpie nest building occurs in five distinct phases. It begins with a muddy, grassy base wedged into the crotch of a branch. Stage two involves adding sticks to form the floor and roof while leaving the sides open. Then a mud base is built on top of the stick floor, which is then lined and finished with fine grasses and animal hair. After the actual nest cup is built, the outer walls are filled in with thorny branches to leave two small openings into the inner nest.

Female magpie carries mud for nest construction (c) John Ashley
Female magpie carrying mud for nest construction
For the most part, males deliver sticks to the nest and build the superstructure, and females do the detailed work of creating the inner nest and cup. But I have seen both members carrying sticks and flying to their nest simultaneously. In subsequent years, old magpie nests are often claimed by raptors. The sturdy stick nests seem to be a favorite for great horned and long-eared owl nests and day roosts at Ninepipe National Wildlife Refuge.

Magpies don't migrate, and pairs usually build their new nest in the same area where they nested last year, just over 900' away (275 m), on average. Like us, most magpies mate for life but are subject to occasional "divorce." Some remain with the same mate for their entire adult life (average 4 years, record of 9 years), and some will pair again if their mate passes away. And about one-third of males and females divorce their partner when they have an opportunity to trade up to a higher quality territory, or home life. Sound familiar?

Males and females both have been documented soliciting extra-pair copulations from neighbors on higher-quality territories. (Unpaired adults don't produce eggs or sperm and don't seek copulations.) An interesting anecdote comes from a researcher trying to catch magpies using a live female decoy. All of the resident females flew in to attack the trespassing female, while male behavior varied. If his mate was nearby, he flew in and attacked the new female. But if his mate was distant, he flew in and courted the female decoy instead. In this example, avian research bore an interesting resemblance to a vice squad sting operation.

Male and females both vigorously defend their nest territory. But magpies often nest in loose groups with territories adjacent to each other, often close to a raptor nest. This was noted by Meriwether Lewis on the first day that the Expedition entered Montana, April 27, 1805 - two hundred and ten years ago.

Earlier that same month, Lewis and Clark packed up "Sundry articles" for shipment from Fort Mandan back to President Jefferson in one trunk, four boxes and four cages. The cages held live specimens of "new" species, including a prairie dog, one sharp-tailed grouse and four magpies. Only one of the magpies survived the four-month trip. Jefferson sent the handsome black and white bird to Charles Willson Peale in Philadelphia, where this magpie took up residence at the first building in the Western Hemisphere to be built specifically as a museum.

None of our other native bird species can make that claim.

Like us, magpies have so-called "vices" that are mostly adaptations for survival. Some adaptive behaviors turn into vices when a society forms and polices what is acceptable behavior within that society. But societies are species-specific (e.g., a magpie breeding population, the citizens of Montana), and we really shouldn't project our rules of behavior onto other animals. So unless magpies start "stealing" broiled chickens from Costco, I'm willing to give them a lot more credit for their interesting behaviors and abilities.