One for Sherlock

Rusty Blackbird - male

A week and a bit ago, when I was down at TTPBRS to allow the coordinator a much-needed day off, we caught a Rusty Blackbird. It was a rather slow morning, we hadn’t caught many birds, so this caused a bit of excitement. Although Red-winged Blackbirds are a dime a dozen, Rustys are the opposite. We see them every season, but in very small numbers, rarely more than one or two at a time, and usually only a handful over the course of the whole season.

This year the water levels are very high on the lake, possibly the highest we’ve seen them in the five years we’ve been there so far. A couple of our net lanes are located close to the water’s edge, and as the water level has crept up, the lanes have become flooded, such that we now require rubber boots to be able to wade in to check them. This is great Rusty Blackbird habitat, as they, like their cousins the Red-wings, are partial to water, and indeed this was the net the Rusty was caught in.

Rusty Blackbird

As we do with all birds, we banded him and took a few measurements and then let him go (after an obligatory, but short, photo shoot). He flew up into a nearby birch where he perched for a few moments, straightening out his feathers and checking out this new accessory on his leg. I couldn’t tell how old he was specifically; most songbirds can be aged as far as whether they were a baby or a parent last summer because of the way the two age classes moult their feathers (adults generally moult everything, while young birds only replace a subset of their nest feathers prior to migrating). However blackbirds are one of those exceptions to the rule, and all I could say was that I knew he wasn’t a 2008 hatchling.

Rusty Blackbird - adult female

In the top photo you can see the rusty tips to the glossy black feathers that give the species its name. We tend to think of a lot of species as having “breeding” and “winter” plumages. In most cases, these breeding plumages are obtained through a second moult in the spring. However, there are a few that only have one moult a year, in the fall, generally before they migrate. Their breeding plumage is obtained through the general wearing down of the feather tips over the winter. European Starlings are a good example of this that most people are familiar with. In the fall the birds replace all their feathers with fresh, white-tipped ones. Over the winter the white tips wear off revealing the oily-black breeding plumage. Snow Buntings are another, rather dramatic example of this type of plumage “change”. In the case of Rusty Blackbirds, their rusty tips wear down to form their black breeding plumage. This individual is an adult female that we banded a couple of years ago in the fall. This year’s male is the first that I’ve banded in the spring. Although we see them both seasons, they’re ordinarily a fall capture.

Rusty Blackbird

Rustys are just migrants through our area. They do breed in southern Ontario, but only once you get up onto the rocky Canadian Shield. There they favour forested wetlands and swamps, particularly fens, bogs and muskeg. In the recently published Ontario Breeding Bird Atlas, the southernmost record for the species were concentrated around Algonquin Provincial Park, a huge expanse of protected boreal forest about three hours north of Toronto, just a few shades shy of Yellowstone National Park in size. They nest as far north as Hudson Bay, where they tend to breed in muskeg along creeksides. They reach their highest breeding abundance in the Hudson Bay Lowlands, where they can be relatively common, though never as abundant even in their peak areas as Red-winged Blackbirds are south of the boreal forest.

Rusty Blackbird - first-year female

Population monitoring surveys such as the Christmas Bird Count and Breeding Bird Survey have shown a rather alarming trend for the Rusty Blackbird. Since BBS counts started in the 1960s, the species has declined by about 95%. Put in other words, only 5% of the population that existed in the 1960s still remains today. The reason for this incredible decline remains a bit of a mystery, as other species that share their habitat and food preferences on the breeding grounds have not shown the same dramatic trends, although many species that breed in boreal wetlands have been declining to some degree. This may be in part due to acidification of boreal wetlands by acid rain (the limestone rock base south of the shield does a lot to neutralize the acids in the water here, but on the shield the rock is granite which doesn’t have the same properties, so groundwater becomes acidic), or, more recently, chemical or physical changes in boreal wetlands as a result of global warming. But it doesn’t explain the huge decrease in numbers of the Rusty Blackbird.

The answer may instead lie on the wintering grounds. In the non-breeding season blackbirds and related species will congregate to roost in flocks of often hundreds of thousands of birds. They target the waste grain left behind in harvested agricultural fields, but also become a pest to growing crops, particularly ripening corn and sunflower seeds. Blackbirds aren’t protected by the same laws of the Migratory Bird Act that cover other songbirds, and they’re often persecuted as agricultural pests. Surfactants are sprayed on roosting winter colonies that disrupt the birds’ natural water-repellent protection, and the birds succumb to the elements. Despite that Rusty Blackbirds don’t actually feed in agricultural fields very often (even in the winter they prefer wet woods for foraging), they tend to join these communal roosts at night, and so are targeted by the same control methods.

Virtually all species of blackbird are in some level of long-term decline (this includes the widespread and widely abundant Red-winged Blackbird, which is nonetheless declining as well). Why the Rusty should have been so dramatically affected when other birds haven’t been is hard to say, and is part of the mystery behind their population crash, however another likely factor is the gradual loss of wet woodland habitat on their wintering grounds as it’s converted for agriculture and development. It may be that a combination of breeding ground and wintering ground factors are coming in to play to cause the species’ decline.

Rusty Blackbird

Because the cause of their decline is still uncertain, it is difficult to form a plan of action to protect the species and bolster its numbers. All we can really do for now is to try to protect the birds on their wintering grounds, maintain the habitat they require there and during migration, and continue to monitor their populations.

It’s sad to think that once upon a time, not so long ago, Rusty Blackbirds may have rivaled some of the other blackbird species in numbers during migration and the winter. Nowadays, it’s a real treat to spot one of these guys as they make their perilous way north and south.

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7 responses to “One for Sherlock

  1. Seabrook-

    Very cool shots, I’ve never been able to see the rusty colored feathers on these birds, thanks for the extreme closeups, so much detail, they’re great.

    Tom

  2. Very interesting post about a bird I am not familiar with at all. I seldom look too closely at the various black-coloured birds.

  3. themarvelousinnature

    Thanks, Ruth. I’m sure if they were as common as Red-wings we’d all be more familiar with them. On the other hand, they’d stick out like a sore thumb if you were watching a group of blackbirds. Despite a really nice swamp at my parents’, my mom has never seen them here, and I’ve only ever detected one, which called as it flew overhead. I think that TTPBRS, being a peninsula and therefore a migrant trap, gets more than most areas usually do.

  4. I’ve heard other reports of deforestation being linked to “diminishing returns” in the bird populations. I feel bad about it — but I still haven’t quit drinking coffee. But 95%!!! I’m gonna hafta at least research which coffee producers are more bird-friendly, and stick to their products.

  5. PS I hope you like the theme song I chose for your blog on Tuesday.

  6. themarvelousinnature

    Lavenderbay: The Rusty Blackbird isn’t one of the species affected by coffee-drinkers, it doesn’t winter far enough south (coffee is grown mostly in the tropics, whereas the Rusty winters in the southern US). So its declines are independent of the coffee trade. However, there are a lot of neotropical migrant species whose declines are in fact in part or entirely due to loss of habitat on the wintering grounds – and some of these are in serious decline. Not to mention the resident tropical birds.

    You’ll want to make sure that the coffee you’re buying is shade grown, which is not as easy to find as you’d think. The bigger catch-phrases when it comes to coffee are organic and fair trade. However, you can pretty easily find Kicking Horse coffee in major supermarkets which, in addition to being Canadian, is shade grown, organic, fair trade coffee. Other specialty (eg. Wild Birds Unlimited, some coffee shops) or online stores (eg. Bridgehead, Birds And Beans – also a store on Lake Shore in Toronto) also carry shade grown. You can also get shade grown tea, though it’s much harder to find.

  7. themarvelousinnature

    Thanks, Tom – having the bird in the hand certainly helps!

    Missed your comment! WordPress has a slightly irritating habit of taking what appear to me to be perfectly normal, reasonable comments, and chucking them in the spam bin, which I don’t check every day.

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