Snowy Owls in Southern Ontario - Studying their diet

Nature Notes for February 28, 2014

What on earth is that young woman doing, digging about in the snow at the foot of a utility pole? If you have stumbled on a scene like this in the past few weeks, you have probably come upon a scientist looking for owl pellets.

The Ministry of Natural Resources is collecting Snowy and Short-eared Owl pellets for a long term diet study to evaluate what they eat during the winter months and how their prey cycles over many years.

So far, the team has found Snowy pellets in Peterborough, Kingston, Wolfe Island, Amherst Island and Dufferin County and Short-eared pellets in Hamilton and Fisherville.

Because very few Short-eared Owls occur in Northumberland County, the rest of this column will be about Snowy Owls. This winter, there have been a number of Snowy Owls in Northumberland County, too. However, these birds have chosen to roost in completely inaccessible locations such as the ice or icy headland at Cobourg Harbour, the ice on Presqu’ile Bay, the ice along the Port Hope waterfront and on the top of farm silos. The searchers have tried, but had no luck finding pellets here.

What are these pellets? Owls usually swallow their prey whole. The birds’ digestive systems collect the indigestible parts of their prey – fur, feathers and bone – into pellets which the birds then spit up. By collecting pellets and tearing them apart, researchers can determine what the bird has been eating.

Snowy Owls nest in the high Arctic where their primary food is rodents called lemmings. In the summer of 2013, the lemming population was very high, so the owls had lots of food. This meant that a higher than usual number of the nestlings survived to leave the nest. However, when winter set in, there was not enough food for so many owls. Many fled south.

This winter, Snowy Owls have been seen throughout eastern North America as far south as Florida.

When Snowy Owls come south, they search out areas which are similar to the ones they occupy in the Arctic. That is, open, treeless expanses. In southern Ontario, this means that they can often be found on windswept beaches, agricultural fields and airports. Most airports have catch and relocate programs for Snowy Owls (and other raptors), since a collision between an airplane and an owl would not be good for either.

Although Snowy Owls favour lemmings as prey on the breeding grounds, they will switch to other prey if lemmings are not available. Other rodents – voles, mice, rats – are acceptable prey. The owl which has been frequenting Cobourg Harbour this winter has learned that ducks can provide a tasty meal. One seen recently on the Port Hope waterfront also had Red-breasted Merganser bits at its feet.

Unlike many owl species, Snowys are active in the daytime. In the long days of an Arctic summer, they have to hunt in daylight.

Snowy Owls are the heaviest of the owls that occur in North America. They are heavily feathered, even to their legs and feet as protection against the cold. As with most raptors, the females are larger than the males. The sexes can be differentiated in the field by the amount of black barring. Females have more barring than the males. Older males can be almost completely white. This was a casting error in the Harry Potter movies, where Harry’s owl, Hedwig (supposedly a female) was played by a clearly small and very white male.

If you know of a roosting Snowy Owl or Short-eared Owl, the MNR team would be pleased to hear from you. Contact Sarah at slmcguire@gmail.com. As I write this, she was busily sorting the bones from collected pellets.

How do birds survive the cold?

Nature Notes for January 31, 2014

Arctic temperatures, ice, wind chill, and blizzard conditions have resulted in Environment Canada issuing many watches and warnings this winter. We are admonished to stay indoors or leave no skin exposed if we have to venture out. For most humans, this has been a winter to stay close to the fire and read.

So just how do birds survive in these conditions? Those that can’t tolerate the cold fly to warmer places for the winter. Others have adapted to survive in frigid temperatures.

Birds are warm blooded creatures, with a slightly higher body temperature than most mammals. They must maintain their temperature or perish. They have several adaptations to help this.

First, they are covered with feathers. Feathers are very good insulators. As cold temperatures approach, birds that stay for the winter grow more feathers, much as a dog grows a denser coat of fur. The small, down feathers which grow close to the skin are excellent insulators. People stuff coats with the down feather of Eider ducks, collected from nests, to keep themselves warm. Often, birds will fluff their feathers a bit, creating small air pockets which add to the insulation.

Feathers are also waterproof, which prevents heat-stealing moisture from penetrating to the skin.

Birds have what is essentially a heat exchanger in their legs. The blood in the arteries going to the feet passes alongside the incoming veins, passing the heat to the incoming blood and hence warming it. As well, birds can restrict the amount of blood going to their feet, which also reduces heat loss. Often the temperature of duck feet will be only just above freezing, while the rest of the bird is very warm.

Sometimes you may see a bird standing on one foot, with the other tucked up into the body feathers to keep it warm. Many birds sit on their feet to warm them. The ducks in Cobourg Harbour often roost on the shore with feet tucked up into their feathers.

Birds must eat a lot of high quality food to maintain their body temperatures. The ice storm which occurred just before Christmas would have been a great hardship for many birds, since their food was unavailable, locked up in a coating of ice. Many birds probably did die, although I have seen a few robins and waxwings, both fruit dependent in winter, since the ice storm, so some survived.

Such species as Blue Jays and Black-cappedChickadees store a supply of seeds for the winter. I have watched Blue Jays make many trips to acorn laden oak trees in the fall. They are storing the acorns above the snow, in crevices in trees or even nooks in a building. My backyard chickadees have many sunflower seeds stored in the cracks in the fence of my backyard. The Gray Jay is well known for caching food, a necessity since this species starts nesting while there is still snow on the ground.

At my backyard feeders, there is always a rush of birds – Black-capped Chickadees and Mourning Doves mostly this year – first thing in the morning. These birds feed furiously to replenish the energy that they have expended overnight just to stay alive. After they have fed, they will seek out a sheltered spot to roost and stay still.

In my garden, a favourite roost of the Mourning Doves is the branches of the spruce tree. Depending on the direction of the wind, the favoured roost may change a bit. If there is sun, the birds will be in the sun, feathers puffed out, absorbing the solar warmth.

Birds use several techniques for overnight survival. Night roosts are in sheltered places, out of the wind. Some species, such as Ruffed Grouse and Snow Buntings, actually dive under the snow. The snow provides insulation.  Groups of cavity nesting birds such as bluebirds, pile into a cavity or nest box. A number of birds in a small space will keep all of them warmer. Chickadees have the ability to reserve energy by putting themselves into hypothermia overnight and pulling out it at daylight.

It really is remarkable that such small animals can tolerate such cold temperatures as we have had this winter. When the mercury drops to -30ºC, as it has several times this winter, I fear that even I become an armchair birder, enjoying the birds from the comfort of my house.

Christmas Bird Counts 2013 - Fighting the Weather

Nature Notes for December 27, 2013

Weather was the major news on the nature front for the past two weeks.

The Port Hope-Cobourg Christmas Bird Count was held on December, an incredibly cold day. The high temperature recorded for the day was only -13º C. An icy wind out of the north-east chilled observers, especially in open locations. There was fog rising over Lake Ontario, so visibility was limited to 100 metres offshore. Snow started in the afternoon, becoming heavy by 3 p.m., which limited visibility even more.

Despite such wretched conditions, thirty-seven observers took to the field, and tallied 15,843 birds of 68 species. An additional 6 species were seen during count week. This was the lowest species count since 1999.

The highlight was a single Great Gray Owl, which was a new species for this count.

Other highlights were: 4 Bald Eagles (tied record high); 1 Red-shouldered Hawk; 231 Wild Turkeys (2nd highest count); 4 Snowy Owls (tied record high); 1 Yellow-bellied Sapsucker; 2 Winter Wrens (tied record high); 2 Ruby-crowned Kinglets; 1 Hermit Thrush; and 6 Common Redpolls.

Low totals recorded were: 19 White-breasted Nuthatch (lowest ever); 892 Black-capped Chickadees (lowest since 2000); and 2 Northern Shrike (lowest since 1993).

Count Week species included: Northern Pintail, American Coot, Thayer's Gull, Iceland Gull,

Lesser Black-backed Gull, and LaplandLongspur.

The following day, December 15, was the Presqu’ile-Brighton Count. If anything, weather conditions were even worse. Added to the bone-chilling temperatures and winds, roads were snow-covered first thing in the morning. Observers were in the field before many of the secondary roads had been plowed, so had to rearrange their planned routes to accommodate the plows. Observers in Presqu’ile Park itself have to walk their routes, so the 15 to 20 cm of snow added to their challenge.

Still, twenty-six field observers and one feeder-watcher tallied 11,320 birds of 69 species. The 11,320 individuals was about half that found over most of the past decade. The 20-year average species total is 79. Waterfowl numbers were low because there was almost no open water inland and Lake Ontario had a wide ice edge.  Only Black Duck and Mallards of the dabblers were recorded.  Long-tailed Duck (365), Bufflehead (57) and Common Merganser (2) were at 20-year lows.  Inland birds were scarce away from feeders and this was the first count in over 20 years that no Ruffed Grouse were recorded.

Several species, recorded in all 10 areas, included; Red-tailed Hawk, MourningDove, Bue Jay, American Crow, Black-capped Chickadee, American Tree Sparrow and Dark-eyed Juncos.

New for the count was a Cackling Goose, upgraded from a Count Week bird in 2012.

Other unusual birds included: 1 Yellow-bellied Sapsucker; 2 Chipping Sparrows; 2 Iceland Gulls; and 1 Glaucous Gull. One Gray Catbird, a Count Week bird, was the first since 1976.

High Counts (old records and years in brackets): Mute Swan - 824 (624 in 2011); Bald Eagle - 8 (6 in 2009); Snowy Owl - 10 (7 in 1978); Dark-eyed Junco - 649 (568 in 2011).

Near-record high counts included Northern Harrier (7) and Red-bellied Woodpecker (5) that missed tying the record by 1 bird each.

This past weekend brought freezing rain. This will probably reduce bird numbers on the first official Rice Lake Plains Christmas Bird Count to be held on January 1, 2014.

The ice coating on everything is not just an inconvenience for humans. It makes the food that birds depend on inaccessible. The many harvested corn and soybean fields that provide food for waterfowl are now under an impermeable blanket of ice. The fruit that is the food of such species as American Robin, Eastern Bluebird, and Cedar Waxwing is now not available to the birds.

Those birds that have enough energy resources will have fled the area. Those that do not have enough stored energy will die.

My bird feeders have been incredibly busy since the ice came. We had to pry them from their poles and let the ice thaw inside in the shower stall in order for the birds to get at the seeds in them. Even the squirrels have been more numerous than usual. Their seed caches, too, are sealed in a blanket of ice.

Now that power has been restored to my part of Port Hope, I can file this column and send to all of my readers best wishes for the coming year. I hope that you all were able to celebrate a Merry Christmas.

Birds of Winter: Bald Eagles, FeederWatch & Christmas Bird Counts

Nature Notes for November 29, 2013

Two large birds were perched in a tree. On closer inspection with a spotting scope, they proved to be two young-of-the-year Bald Eagles! A better perspective of their perch could be found from a bit further down the road. From there, we could see that the eagles were being harassed by five Common Ravens. Then, three coyotes trotted through the scene. The local flock of American Crows was keeping a respectful distance from the eagles.

Were we in Algonquin Park? No. This scene played out along a road just south of Roseneath in Northumberland County last Tuesday, November 26, for five delighted observers. Probably, out of sight from the roadside, was the carcass of some dead animal, perhaps a deer, on which all of these animals were feeding.

Otherwise, this birding expedition was very quiet. Even Black-capped Chickadees were present in smaller numbers than usual. The cold temperatures of the past few days have frozen most marshes, small ponds, and even the quieter bays of Rice Lake. Now waterfowl can be found only on the open water of Lake Ontario.

At feeders, even American Goldfinches are scarce. The other finches that sometimes arrive in winter will probably not come this winter. Observers in the northern forests report an abundant seed crop. Pine Siskins, Common Redpolls, Evening Grosbeaks, and Pine Grosbeaks which feed on these seeds will not have to come south to eat well. Although there have been a few American Goldfinches in my garden, they have been feeding on the cones of the white cedar and the seed heads of the purple coneflower, not on the niger seed in the feeder.

Another Project FeederWatch season has begun. So far, the most abundant bird in my garden has been Mourning Dove. Several days, there have been 20+ doves in a rather small space. When the sun shines, after they eat their fill, they find the sunniest spots to roost. They are very difficult to see against fallen leaves, dead grass and the gray branches of the brush heap. With so many doves present, it probably won’t be long before a Cooper’s Hawk finds the yard.

Up to five Blue Jays have been frequenting my feeder. Their preferred food is corn, which I scavenged from my family’s harvested corn field.

In the past week, 2 Downy Woodpeckers, 1 Hairy Woodpecker, 1 Red-belliedWoodpecker and a Yellow-bellied Sapsucker have visited the yard. All but the last will stay through the winter. Although a few sapsuckers sometimes persist through the winter, most migrate to the southern U.S. and Mexico.

There has been a flock of up to five Northern Cardinals hanging around the yard. Although they are not especially unusual here, I don’t often see so many at a time.

The last stop of the birding group mentioned at the beginning of the column was an overlook of a frozen bay of Rice Lake. There, we found a third Bald Eagle, flying past and north over the islands towards Peterborough.

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Before the next Nature Notes appears, two of Northumberland’s Christmas Bird Counts will have taken place. The Port Hope-Cobourg Count will be held on December 14 and Presqu’ile-Brighton’s on December 15. The new, officially sanctioned Rice Lake Plains Christmas Bird Count will be held on January 1, 2014.