Two minds meet in a parking lot

Haines Ferry Terminal, Haines, Alaska

I had just pulled the van into the ferry queue and stepped outside when they arrived: from the tree-tops of the nearby Pacific Northwest temperate rain forest, two Northwestern Crows (Corvus caurinus) glided and landed on the asphalt beside me. Hopping to a stop and quickly re-arranging their wings, they looked up at me and I looked down at them. In a moment, with our mutual glances, it was obvious that these two were here because of the growing line of cars, vans and campers that were parked, lining up to board the evening ferry to Skagway, Alaska. I decided to watch.

Earlier in the evening, I had glimpsed a pair of Northwestern Crows foraging by the ocean as I was driving along the coast of the Lutak Inlet to the ferry terminal. As the common corvid of the coast in this part of North America, it wasn’t a surprise to see them here. The tide was receding along a rocky beach, and as I passed, the crows appeared from the shoreline below. Their wings beating in the stiff on-shore breeze with the kind of tempo one expects when birds take flight, they both flew up into a sharp parabola. One of the pair had something in its bill—it looked like some sort of mollusc—and slowed down its wing beats, quickly decelerating. Reaching the apex of its flight, it dropped the object from its mouth onto the rocky shore below. Down the birds flew, on I drove.

This kind of behaviour isn’t unusual in the Northwestern Crow. They’re known to be foragers along the edge of the ocean, looking for aquatic organisms that become stranded as the tide ebbs. If it can be found between the exposed rockweed, it can be considered food and these crows find their protein in the fish, molluscs and crustaceans that live along the coast of the Northern Pacific. While they are foragers, and live commensally with humans, I experienced something unexpected along the line of vehicles.

Northwestern Crows

As I watched the crows standing at my feet, they hopped past me and my vehicle towards the van that had pulled up behind mine in the queue. With what I would describe as curiosity, the two crows began to inspect the grill of the camper van. It became clear what they were looking for: insects. Or, more correctly, they were searching out freshly-deceased insects that had stuck to the camper’s metal and chrome. And so the metal grill became the shore: up these birds flew, gleaning the remains. Because of the lack of a good perch, they looked more like oversized Ruby-Crowned Kinglets (Regulus calendula) feeding in this way, with their wings quickly flapping to give them the purchase they needed to get their food. This was challenging work for the crows. After the “easy” carcases were gone, it became a cooperative effort with each bird taking turns in one of two roles: one flying up to remove the insects and the other, after the insect hit the pavement, eating it up.

In the minutes before the ferry arrived they continued looking for more to eat, moving from car to van down the line of vehicles.


Fragmented & Young Forest preferred by Migrating Songbirds

Black-throated Green Warbler
Creative Commons License photo credit: Jim Frazier

Research published in Vol. 126, Iss. 3, pg. 579 of The Auk has some interesting implications for habitat conservation for migrating bird species here in eastern North America. In short, during Spring and Fall migration, migrants showed no preference for stopover locations based on distance from a continuous, connected (river corridor) habitat, nor were they more likely to be concentrated in one forest patch over another. Plainly, the migrating birds appear to show no preference for connected habitats versus fragmented ones. Clearly, if this is the case, birds are using other criteria to select where they stop while migrating.

What is interesting, and not surprising, is the finding that during Fall migration, birds do select habitat described as “early succession forest” with high density of native and non-native fruit-bearing trees and shrubs. In the cannon of conservation, habitats that are fragmented or in the early stages of succession are seen as lower quality when compared to continuous and stable habitats. And this may still be the case when it comes to nesting (less nest predation in larger forests, for example)—but it would seem as though we might need to re-evaluate the assumption that these younger, more fragmented landscapes are of little or no use to birds and ultimately, bird conservation.

As migratory stopovers, it would seem that all forested landscapes—no matter how mature—are important.


Female Blue Tits use home-made potpourri in nests to to attract males and have healthier chicks

Blue Tit by Marko_KBlue Tit used under a creative commons lisence by Marko_K. Thanks Marko!

Blue Tits (Cyanistes caeruleus) nesting on the Medeteranian island of Corsica have been known to incorporate fresh sprigs of aromatic plants, like French Lavender (Lavandula stoechas) into their nest cups. New research ((Aromatic plants in nests of blue tits: positive effects on nestlings by Adèle Mennerata, Philippe Perreta, Patrice Bourgaultc, Jacques Blondela, Olivier Gimeneza, Don W. Thomasc, Philipp Heebb and Marcel M. Lambrechtsa)) reports that there may be benefits beyond a nest that smells like potpourri: these aromatic plants offer benefits to larger broods of Blue Tit chicks.

The potpourri, interestingly, does not reduce the number of ectoparasites ((Corsican Blue Tits hold the distinction of having the highest known “loads” of blow fly larvae, for example)) found on the birds in the nest. Rather, the researchers suggest that either the aromatic plants offer immune system benefits (mechanism still unknown) or, and I quite rather like this idea, the females that actively incorporate fresh sprigs of aromatic plants are indicating their fitness to males. In other words, the fresher, more aromatic the nests, the “better” the female is as a mate (and subsequently, the “better” the offspring).

Now that makes you think about that stale bowl of potpourri on the back of your great-aunt’s toilet tank differently…


Double-crested Cormorants self medicate by swallowing stones

Double-crested cormorants (Phalacrocorax auritus) in silhouette

Thanks to Flickr member mikebaird for sharing the DCC photo with a creative commons license.

A just-published paper suggests that Double-crested Cormorants (Phalacrocorax auritus) in the Great Lakes may swallow stones to reduce the number of parasitic nematodes–and in so doing, are self-medicating. Many birds ingest stones to help with the digestion of physically hard objects, but fish, the primary meal of the DCC are soft-bodied and don’t need the kind of mechanical assistance. So why are DCCs found with ingested stones?

Researchers found that:

At a Lake Ontario site, females more often had small stones in their stomachs and were less parasitized by nematodes than were males, and males with small stones had fewer nematodes than males without small stones. We did not find similar patterns in small stone presence or parasitism at a Lake Erie site; however, Lake Erie birds had fewer parasites and lower proportions of birds with small stones.

Which, in turn lead to the conclusion that since the birds that had stones were less likely to have nematodes, then the stones are the bird-equivalent of some anti-worm medication. Smart birds.

Small rant:

Interestingly, the Lake Ontario site was located at Presqu’ile Provincial Park and the Lake Erie site was located at Middle Island, Ontario. These are two sites where DCC culls have taken place in the recent past, with websites reporting a May 2008 cull on Middle Island that matches with the date in the paper’s method section. I can’t find any mention in the paper to the “source” of the birds or how the birds were “collected”.

Some may say there is no space for politics in scientific research and regardless about your feelings about recent DCC culls, I think that because the article makes no specific mention of how and where the researchers got their DCC gastrointestinal tracts, it does nothing but reduce the transparancy and therefore, the quality of the work.


Spring feels around the corner: things are moulting away…

The past two days in Toronto have been warmer than normal, leading to a large snow melt and the promise of spring (and I know it’s a tease, but it’s a nice break from what has felt like an especially cold winter). With spring comes the return of migratory birds, so this research seems relevant.

First, some background. Feathers, unlike our bones, lack an ability for self-repair. They can be attacked by feather-loving bacteria ((Better described as bacteria that degrades the Keratin, the protein that makes up the feather.)) and suffer from UVB damage (and sunblock doesn’t really help out). So birds moult, or replace feathers, up to twice a year. According to my Sibley Guide to Bird Life and Behaviour, most North American birds replace feathers in a complete moult in the late summer or early fall. Some birds undergo a second moult in the spring, before the breeding season.

Birders out there have experienced these two moults when faced with confusing fall warblers: males no longer are in their colourful, easy-to-identify plumage (which appeared during the spring moult) and we humans suffer under the burden of having to learn, what could easily be described in some cases, as a whole new bird.

Willow Warbler
Creative Commons License photo credit: Taz-Voll

Why there is a difference in moults is the subject of this research by Thomas P. Weber, Johan Borgudd, Anders Hedenstram, Kent Persson & Garan Sandberg. Comparing the mechanical strength of flight feathers from two species of similar birds that have different moulting strategies, researchers found that the bird species that moults twice ((In this case, the willow warbler, Phylloscopus trochilus, which is a small European insectivore.)) have comparatively weaker (more prone to fatigue) feathers than the species that moults once. Since the authors suggest that “the species with feathers that fatigue faster moults twice annually and not once” it would seem the willow warblers moult out of a form of necessity: they would suffer from the consequences of weakened feathers as they migrated to or from their breeding territory.

Now, if this feather weakness is a similar case for birds of the Americas that moult twice, it’s interesting to note that Wood Warblers (Family Parulidae) also change the colour of their plumage with the two moults. Because of this breeding plumage / winter plumage dichotomy, it would seem that feather weakness isn’t the only reason why a bird would moult twice. The interesting question would be if the adaptation to two moults a year “allowed” wood warblers to have a colourful breeding plumage–the ability for males to “change” their appearance for the breeding season and visually demonstrate just how fit they are.


Knowing me, knowing you

Coming in for a landing

If you’ve ever spent time watching House Sparrows (Passer domesticus), you might have noticed just how, well, squabbly they can be. Just today, I was out walking the dog, and a group of three came screaming (in flight and in sound) out from a pruned cedar shrub, flew across the sidewalk and screamed back into another shrub. They’re social little birds and use that sociality to their advantage–often relying on others to find food to eat. Fights between birds erupt over a number of different reasons (just like us, really) and food is often a source of conflict.

A recently-published paper in the journal Animal Behaviour ((Source Details: Zoltán Tótha, Veronika Bókonya, Ádám Z. Lendvaib, Krisztián Szabóc, Zsolt Pénzesc,and András Liker (2009). Effects of relatedness on social-foraging tactic use in house sparrows. Animal Behaviour, 77(2), 337.)) reports the results of a study that looked at the effect of how being related to another House Sparrow might effect reactions over food.

The study suggests that the more closely related an individual House Sparrow was to another, the less likely there would be conflict (called “Aggressive Joining”) over food. If there was conflict with a close relative over food, less food would be taken from that relative.

Interestingly, there was a sex difference reported that was possibly attributed to the fact that female House Sparrows spread out over a greater distance from their original flock. If a male was to take food without conflict from another bird, it was always from a non-relative bird. Females, however, showed no discrimination when they were taking food (without conflict) from others. Since it is females that spread out, they’re less likely to have close relatives in their new flocks–hence they show no preference for taking food from close relatives or non-relatives.

Perhaps most interestingly, but not surprising, was the acknowledgement that House Sparrow have to be able to recognize and know close relatives:

Since we found differences between several aspects of scrounging behaviour towards close kin and nonkin birds, sparrows are likely to be able to distinguish between genetically closely related and unrelated flockmates.

Since House Sparrows neither breed co-operatively or form family groups, their ability to recognize close relatives is seen as significant.

So, now, while you’re sitting on a patio this summer and see House Sparrows at your feet, spend some time watching them and their reactions over food. You might be able to decide if they’re close relatives or simply strangers.

Birding Birds

First Impressions of the First Edition of Peterson Field Guide to Birds of North America

I went to the book launch of the Peterson Field Guide to Birds of North America yesterday (pictured on the left) and I was struck by a couple of design decisions that I think are a bit peculiar. While my caveat emptor is that I spent about 5 minutes leafing through it, two one deficits jumped out at me immediately:

The first is size. The book has grown and now is more in line with the original Sibley’s guide (the website has the book dimensions listed as 6×9 inches). For me, a book of this size no longer becomes a field guide–a book that can easily slip into a coat pocket and is forgettable as you carry it around–it becomes a desk reference. Yet, right there on the cover is the fact that this is supposed to be a field guide. Sibley’s guide as a desk reference is “worth it” in my opinion, because the extra space is used to describe and illustrate a wider variety of colour morphs seen across North America. In the new Peterson guide, the bigger pages are filled with larger illustrations. I don’t know if this is a demographic decision (Houghton Mifflin: “Birders are getting old. We need to make the bird illustrations bigger so they can see them easily”), but I was somewhat surprised that the new edition is essentially an old Peterson Field Guide “super-sized.”

Second, range maps are in the back of the book. Another bone-headed move on the design front. Having to flip around a book to try and find if what I think I’m seeing should actually be where I’m seeing it is extra effort. This is actually a step backwards for the Peterson guides because in the most recent edition of the Eastern guide (and I have to assume Western, too) there are range maps right on the same page as the plates. All the “current-generation” bird books that I own have range maps right with species descriptions and plates. The only reason why I can think the move was made has to do with the size of the maps: they’re much larger then they would have been if they were to have been included with the text. Personally, a small map never was much of a limiting factor when using a guide.

Update (09-11-08): As per the first comment below, it would seem that I managed to miss the inclusion of range maps beside the species descriptions. So, it would appear that you get flip-free small range maps and the larger range maps in the back.

This guide is supposed to assume the mantle of the new edition of Peterson bird guides. I suspect that Houghton Mifflin will, à la Sibley Guide to Birds, publish more compact regional versions (previous Peterson guides covered Eastern and Western North America) of this guide sometime in the future. It’s an interesting plan because while this worked for the Sibley guides, I’m not so sure it will work again in the case of Peterson. My resoning is this: at some point people don’t need another field guide. There was enough value-added in The Sibley Guide to Birds to warrant having both a desk reference and a field guide. I don’t see any extra value in owning the first edition of the North American Peterson and a field-guide size regional version too. It will be interesting to see what the future holds for this edition.


Birds migrate at night in loose flocks

Birds migrate at night. Bird tend to flock together.

These two disseparate facts have been recently weaved together to suggest that birds migrate at night in flocks. What I find interesting here is the suggestion that these flock are “loose”–not the tight configurations visible in the preceding video of starlings flying in a flock–birds may be migrating in groups that are as much as 200 meters apart from each other. As the lead researcher, Ronald Larkin, suggests birds flying in the same direction at one point in time is not the same as birds travelling together over long distances:

“Even back in the 1970s it hit me that you can have two birds flying absolutely parallel in the same direction and at the same height, but they can be flying at such a different speed that one of them gains on the other and they’re just, you know, automobiles passing on the expressway,” he said. “They’re simply taking the same route and not keeping together.”

What Larkin has shown through a magic elixer of radar and statistics is that migrating birds tracked were actively travelling together: same speed, same altitude, same direction. Just much further apart then we had ever imagined before.

For me, this finding brings up the obvious question: how? I know I’ve stood outside during spring and fall migration and heard the whisper thin call of migrating passerines, so perhaps they stay in contact via vocalizations. But that’s just conjecture on my part.

And I have to share Larkin’s sense-of-wonder with this phenomenon:

“To me, that’s the marvelous thing – that they’re flying in social groups in the middle of the night in the middle of the air, over territory most of them have never been over before.”

Link to article

Academia Birds

Prairie Chickens and bird-watching

I keep an eye out for newspaper articles published on birding as I find they provide an interesting insight into the larger cultural perception of the activity. While I’m not doing a discourse analysis of this stuff, a recent article published in the New York Times (Prairie Birds Flirt, and a Town Livens Up) hits on some interesting themes that I’ve been finding in my research.

Certain birds have agency in attracting humans

The article outlines the fact that the bodily presence of Prairie Chickens attracts humans. Following the normal pattern, it is the fact that these birds are perceived as being rare that attracts birders to come and see them. Rarity isn’t the only reason that birders are interested in these birds, aesthetics plays a large part in attracting humans–the Prairie Chicken’s spring-time display, visually stunning is a key component. This mating display between males is unique to one time of year and so rarity is compounded–an aesthetics that is rare in time in addition to the Chicken’s diminishing numbers.

Birds, then, have positive impacts on local economies

Humans travelling to take in the display has had an positive, significant impact for the local (human) economy. Animal agency becomes bird tourism, where birders travel and spend money in the same area that these birds are being seen. Since the agricultural economy in the region has softened, this is seen as a positive influx of money for the local economy–money spent on lunches, gas and accommodation.

Ironically, the Prairie Chickens are in this sparsely populated region for the reason that humans are not–the birds need undisturbed prairie habitat. No mention is made in the article how the increased attention on the birds with impact the number of birds in the future. Likely, there’s the rosy forecast that more attention paid to the birds will improve their profile and, in turn their numbers. Quite often, however, this conclusion is made without any real interrogation of the potential birder’s impact.


Acadian flycatchers prefer the country to the city to nest

Urban birds that nest in wooded areas don’t do as well (reproductively-speaking) as their non-urban counterparts. Conventional wisdom suggested that this was because of the presence of more egg-eating predators (eating bird eggs, obviously) in urban settings. New research suggests, however, that it might have more to do with fitter (larger, older) birds preferring (and getting) larger, non-disturbed wooded areas:

Urban areas attracted lower-quality birds which, compared to those in rural areas, arrived later in the spring, left earlier in the fall, made fewer nesting attempts and were much less likely to return to nesting spots from year to year.

Acadian flycatchers (Empidonax virescens) were the bird species studied, and it would seem that the urban flycatchers managed to raise one young versus two in the case of the non-urban flycatchers. Knowing just what makes these urban spaces unappealing to these birds is unknown. The brown headed cowbird (Molothrus ater) is a nest parasite–meaning that it lays eggs in another species’ nest and lets those birds raise the cowbird’s young–and is suggested as perhaps playing a role here. Urban nests were two times more likely to be parasitized than rural ones.