Thursday, 18 January 2018

Another Take on Snowy Owl (Harfang des neiges) Movements

     The other day, while killing a little time on a visit to Windsor, ON Miriam and I dropped into a bookstore (isn't that what every sane person does?) and I picked up a copy of The Thing with Feathers by Noah Strycker. It is filled with chapters about different birds with a multifaceted examination of their behaviour (part of the subtitle for the book is The Surprising Lives of Birds)and, about a third of the way into it, I have found it both entertaining and informative.
     I was especially struck by a chapter called Snow Flurries about Snowy Owl (Bubo scandiacus) behaviour and its relevance to the area in which I live, where this magnificent denizen of the arctic tundra is a regular winter visitor, sometimes in substantial numbers.

     It confounds some of my friends that we are able to see this species with such ease, and I suspect it causes not a little unseemly drooling!

     Conventional wisdom has often advanced the notion that movement into the south (south for the bird that is) has been triggered by a shortage of food in the arctic, especially in irruption years, when the presence of large numbers of owls has been attributed to crashes in the Brown Lemming (Lemmus sibiricus) population. See the following references:

North American Owls, Paul A. Johnsgard (1998):  ....incursions......generally occur at intervals of about 3 - 5 years, coincidentally with cyclic or periodic declines in lemming populations.

Owls of the World, Edited by John A. Burton (1973): It is a decline in the availability of prey, ......that is a cause of Snowy Owl irruptions.

The Owls of North America, Allan W. Eckert (1987): Migration is extremely cyclic and predicated on the availability or nonavailability of prey.

Owls, Tony Angell (1974): The migrations are stimulated by the shortage of their principal foods, lemmings and Snowshoe Hares.

     The diet of Snowy Owls, however, is varied and includes other rodents, ptarmigans, songbirds and waterfowl. In the winter in southerly locations a Snowy Owl is very opportunistic and will take whatever prey is readily available. This female is eating a Mallard (Anas platyrynchos) in Bronte Harbour, Oakville, Ontario. For birds that regularly winter at this location, waterfowl forms the principal items on the Snowy Owl menu.

     Snowy Owls are nothing if not peripatetic and have a highly nomadic lifestyle. Strycker cites the example of seven chicks banded on Victoria Island in northern Canada, three of which were subsequently relocated at Attawapiskat, Ontario (2,050 km), Clyde Forks, Ontario (3,250 km) and Sakhalin, Russia (5,300 km). These movements are seemingly unrelated to seasonal food shortages and reflect the inherent behaviour of an avian nomad. In fact Snowy Owls seem to manifest little or no inclination to site fidelity at all.
     To return to the question of whether precipitous declines in lemming populations are the reason for mass Snowy Owl movements to the south, it appears that exactly the opposite is true, borne out as Strycker points out, by rigorous statistical analysis of both the biomass of lemming prey and the movement of owls.
     All the evidence points to Snowy Owls having a highly successful breeding season in years of lemming abundance, rearing seven or eight chicks in an average nest, a prodigious feat indeed. When these young birds fledge, there are not enough territories to go around and this is what triggers a mass migration south, and results in the spectacular invasion years we sometimes see in southern Ontario, where in an exceptional year it is possible to count twenty-five Snowy Owls in less than a forty-five minute drive from my front door.
     So, it is a bonanza year for lemmings that stimulates mass migration from the tundra, not the opposite.
     There is support for this assertion in the literature:

Owls of the World, Rob Hume (1997): When the population reaches a peak after a good breeding season, more owls will move south, especially young birds working hard to survive their first winter.

Owls of North America and the Caribbean, Scott Weidensaul (2015): Although most people assume that hunger drives irrupting owls south, in major Snowy Owl invasions the cause is usually extraordinary plenty, not privation.

     I would like to end this short piece with a plea to my fellow birders, and especially those who in recent years are far more likely to carry a camera with a huge lens. Please, do not trespass on farmers' fields to get closer to the owl. This causes problems for others, especially those of us who have working relationships with farmers who permit us to study birds on their property, causing them to become resentful of the birding community and withdrawing our privileges. Furthermore the owls are resting between bouts of hunting, and disturbing them so that you can get the perfect flight shot causes them to expend valuable energy unnecessarily.
    The same admonitions apply to birds found in harbours. Do not try to gain access to private docks where you have no business trespassing. Think of the whole picture and not just your desire for a better image.

      Enjoy the bird at a respectful distance and consider yourself one of the lucky few able to spend time with this iconic bird of prey.

Wednesday, 17 January 2018

Book Review - Far From Land - Princeton University Press

     After due consideration, looking back on my life, if I had it all to do again, ignoring prior restraints that would have in reality mitigated against such a choice, I would be a seabird biologist. Little, it seems to me, could have much greater appeal than to get paid for researching what is surely one of the most fascinating group of organisms on earth - or should that be at sea?
     Thus it was with great pleasure that I received an advance copy of Far From Land (a lovely, evocative title to be sure) for review. Not only did the subject hold instant appeal, it was heartwarming to see that its author is Michael Brooke, whose output I have long admired by way of his prior work on albatrosses and petrels, and his co-editing of The Cambridge Encylopedia of Ornithology. along with Tim Birkhead. This was akin to an aficionado of a novelist getting his hands on the next title. And I read it with the same voracious enthusiam!

     Through Brooke's eyes I would relive the incredible excitement, and emotional high, of my first albatross in the Benguela Current off the coast of South Africa, one of the richest feeding grounds for pelagic species in the world.
     Michael Brooke writes with all the expertise and knowledge of a seasoned biologist, consolidating years of research into one easily readable book, but displays a wry sense of humour, unrevealed in strictly scientific works. The format makes a complex topic accessible to a reader with even a bare minimum of prior knowledge.
     It has always been relatively easy to track landbirds, with devices as simple as a metal band placed on their leg with an identifying number, and even though the recovery rate is minimal, information is built up over time as to the migratory patterns of numerous species, with inferences on routes taken, flight speeds, stopover areas, and other useful information. Consider for a moment the near impossibility of tracking seabirds, who spend the bulk of their lives far away from land, traversing and sometimes circumnavigating the globe. A metal band is as likely to wind up in the stomach of a shark as to be recovered ashore.
     The development of mini satellites and the increased miniaturization and sophistication of trackers (and other devices) has now made it possible to follow seabirds on their peregrinations around the globe. Many prior held assumptions about migratory routes have been dispelled and new information has been gathered about the different dispersal and feeding patterns of adults versus juveniles. Data has been amassed and analyzed on the mix of birds feeding in areas with changing productivity layers - and countless other topics, all organized in chapters following on one from the other.
     There is an extensive bibliography for each chapter, enabling anyone with sufficient curiosity to explore these topics in far more detail.
     The text is enough to satisfy the discriminating reader, but an added bonus is a series of exquisite illustrations by Bruce Pearson, a wildlife artist whose delicate touch is well known to many natural history enthusiasts.

       I found this art especially pleasing and it added measurably to the enjoyment of the work. 
      And to cap it all, I discovered a new word.  The word is rumbustious, defined in the Oxford Dictionary as "noisy, boisterous, uproarious." This descriptive is used by Brooke to denote the attitude of a bird he was handling, but perhaps seabird biologists like him are a tad rumbustious at times. Would that I were one of them.

Publication date: 21 March 2018     Price: 29.95

Tuesday, 9 January 2018

Tuesday Rambles with David - Riverside Park, Cambridge, ON

09 January 2018

     Riverside Park is a multi-use park in Cambridge, ON which we have driven past scores of times but have never investigated as a potential location for our birding walks. Francine and Jim were in the area recently on the way to visit Jim's dad when they decided to stop in for a brief visit, and we are all glad that they did, for it is a fine spot to do some birding, with several varied habitats. It holds the promise of rewards year round, and we are determined to return often.

     Franc and Carol are away until mid February in Arizona and Mary is cross country skiing for the week in the Algonquin area, so Judy, Jim, Francine, Miriam and I set out for a Tuesday adventure, happy that the brutal cold snap of late had ameliorated, and it was a pleasant winter's day. We were happy to resume our regular walk after an absence of a couple of weeks.
     We started to see birds right from the very beginning of the trails, assisted in no small measure by bird seed deposited at various intervals by kind citizens anxious to give our feathered friends a helping hand during dangerously cold spells.
     Downy Woodpecker (Dryobates pubescens) was quite common and approached us fearlessly at close range.

     But first place went to American Tree Sparrow (Spizelloides arborea). These delicately beautiful little birds seemed to be visible at every turn, and I don't think I have even seen so many in one place. Truly it was magical.

     Groups of birds in mixed species flocks took advantage of an easy meal; Francine and Jim had brought bird seed with them, and liberally spread it around.

     The park looked sombre clad in its winter dress.

     Northern Cardinals (Cardinalis cardinalis) were ubiquitous and provided a vivid burst of colour against grey and leafless branches.

     The female of the species is a little more muted, but nonetheless beautiful.

     Behind her you can see both American Tree Sparrow and White-throated Sparrow (Zonotrichia albicollis), the latter being relatively unusual in winter.
      A male House Finch (Haemorhous mexicanus) is a study in colour at any time, but in the winter it stands out most vividly.

     American Robin (Turdus migratorius) is the species that most people view as the traditional first bird of spring and many eagerly look for the first sighting around early March as the birds move back from the south. With ever greater frequency, however, numbers of this species are choosing to spend the winter here, exploiting micro climates and taking advantage of every food source available. It was with great pleasure, therefore, that we encountered robins several times, but it is no longer to be totally unexpected.

     These individuals were feeding on the berries of European Buckthorn (Rhamnus cathartica).

     Does this image of a male Northern Cardinal in the northern woods not stir the heart of every naturalist? Is beauty more sublime?

     Dark-eyed Junco (Junco hyemalis) is a feature of the winter landscape, many of them are puffed out against the cold. I think any child passing by would want to cuddle this rotund little fellow.

     More trails in the park beckoned us.

     One of the real surprises was the presence of a male Red-winged Blackbird (Agelaius phoeniceus). While I have seen this species in the winter before, it has been extremely infrequently, so if there is such a thing as the bird of the day, this may have been it.

     The presence of a House Sparrow (Passer domesticus) feeding with the blackbird was less of a surprise!

     I am not sure how many White-throated Sparrows were seen, but I suspect at least three. It is a handsome bird indeed, and dear to many Canadians, for its haunting song is often rendered "Sweet Canada, Canada, Canada."

     As you would expect, Black-capped Chickadee (Parus atricapillus) decorated every tree, cheerful and totally fearless.

     It seemed that we could not travel far along the path before another friendly Downy Woodpecker would appear, often stopping to feed.

     I have little doubt that Pileated Woodpecker (Dryocopus pileatus) is present but we did not see one. Here is evidence of ancient excavations by this species.

     More American Robins travelled through the trees alongside us.

     We meandered along several trails, exploring the area, and making mental notes about promising areas during spring migration.

     It is astounding that the tiny Golden-crowned Kinglet (Regulus satrapa) survives the winter here, but regularly small numbers remain in the province. It bears remembering that we have just emerged from a spell of savage weather, when overnight lows dipped to as low as minus 32 degrees. 

     The nasal call of the White-breasted Nuthatch (Sitta carolinensis) often betrayed its presence and it was not at all shy in visiting us at close range.

     Perhaps the American Tree Sparrows and White-throated Sparrows had enjoyed seeing us as much as we had enjoyed seeing them, and had enjoyed the food we provided for them, for they came to bid us adieu.

     We have already decided that we will return to Riverside Park next Tuesday, so with luck we'll see them again.

All species: Mallard, Red-tailed Hawk, Mourning Dove, Downy Woodpecker, Blue Jay, American Crow, Black-capped Chickadee,  White-breasted Nuthatch, Golden-crowned Kinglet, American Robin, American Tree Sparrow, Dark-eyed Junco, White-throated Sparrow, Song Sparrow, Northern Cardinal, Red-winged Blackbird, House Finch, American Goldfinch, House Sparrow.  Total: 19

Wednesday, 3 January 2018

Book Review - A Taste for the Beautiful - Princeton University Press

    It was at an opportune time that I received this book for review, having recently embarked on the task of reading for the third time the seminal works of Charles Darwin, whose ideas transformed all previous notions of the origin of species, and challenged the universal belief in divine creation.

     In many ways, Michael J. Ryan's research takes over from Darwin's The Descent of Man, and Evolution in Relation to Sex. It expands on Darwin's original theories and clearly identifies that the brain is the organ specifically adapted to developing a taste for beauty. More specifically, it is the female brain.

     By reinforcing a clear preference for a male characteristic that provides prima facie evidence of superior genes, females that preferentially mate with such males ensure that those attributes are perpetuated and enhanced in subsequent generations.

     Think only of the bizarre tail of a male Peacock and the disadvantage it must pose to the male, yet it indicates to the female that the possessor of such ornamentation is parasite resistant, and in other ways healthy, to cope with what at first blush seems like an impediment. Since males with the finest tail feathers and the most vigorous display will attract many females, thereby assuring multiple matings, they will succeed in passing on their genes. And the male offspring from such pairings will inherit the splendid tails of their fathers.
     A taste for beauty is not limited to non-human animals and has wide ramifications for our own species. Not only is physical beauty a criterion for humans, but the ability of a very wealthy man to acquire what is sometimes referred to as a "trophy wife" is a clear indication of a woman choosing a man old enough to be her father, because he is able to provide financial security and all of the pleasures of life. In virtually all cases it is the female who makes the decision in such arrangements, not the male.
     Michael Ryan is a serious scientist with a wide body of work, but he has written this book in a style readily accessible to the layman. Wonderful black-and-white illustrations begin each chapter.
     It is a very fine work; you will never think about beauty and attraction in the same way again.

Publication date: 07 February 2018

Price: US$27.95, £22.95