Sunday, January 27, 2008

Birds in Winter Storm Events

Photograph by David Powell

The New Mexico New Year’s Eve snowstorm of 2006-07 dumped record amounts of heavy, wet snow statewide, snarling traffic throughout the state, creating a run on, and subsequent shortage of, snow removal equipment, and emptying the produce shelves of supermarkets. Although most humans were merely inconvenienced, others paid for this storm with their lives. The economic hangover of this storm will not be as easily vanquished as the more traditional headache and queasy stomach that often accompany the Rose Bowl parade.

The Office of the Medical Investigator (OMI) attributed the deaths of 16 individuals to the storm as of January 7, 2007. Ten death were caused by vehicle accidents related to driving on snow and ice; three stemmed from carbon monoxide poisoning; and another three were from exposure to cold. Cattle losses remain difficult to fully quantify because ranchers have still not been able to reach all of their livestock. The true number of livestock deaths may not be known until spring. Costs incurred by the state, local governments, and schools associated with emergency protective measures and snow removal will approach $10 million, and lost economic activity primarily related to highway closures and reduced productivity is estimated to be tens of millions of dollars.

Although the record snows of this winter will provide better habitat for the spring breeding season, the dense snowpack limits the ability of all animals to find forage. The food shortages that ravage pregnant livestock are equally brutal on pronghorn antelope, elk, deer, sheep, and even more so on small mammals such as jackrabbits and cottontails. For land-locked mammals, flight in the face of an approaching storm is an impossibility, and finding shelter in the short grass prairie can be a daunting prospect. Animals that take refuge in underground burrows may be buried beneath several feet of drifted snow. Storm related avian deaths of small birds cane be difficult to quantify; however, mortalities of larger birds that concentrate in limited areas, such as waterfowl and waterbirds, are well documented. One can assume that the smaller, and less detectable songbirds suffer similar mortality.

Storm related trauma was reported in several species following a blizzard that struck the Midwest in late March, 1996. A rainstorm that quickly changed into a snowstorm with winds in excess of 60 mph contributed to the death of 2,000 Sandhill Cranes in Nebraska's Rainwater Basin, 7,000 coots and ducks in northern Iowa, and 9 Canada geese in Wisconsin. There were also unconfirmed reports of storm related mortality of waterbirds and migrating passerines in surrounding states.

The USGS reports the storm-related deaths of 1,900 Eared Grebes in southern Utah in 1997. Apparently, the grebes became disoriented during a snowstorm and mistook snow covered fields and streets as water, and attempted to land. Over 2,700 additional grebes were rescued and returned to a nearby refuge.

In Iowa, there was a 70% reduction in Ring-necked Pheasant following a severe winter blizzard in 2004 that dropped 23" of snow. In 2005, a die-off of birds was reported in Yellowstone National Park in Wyoming following a severe spring snowstorm blew nearly 50,000 birds into the park. Of these, 127 individuals of nine species succumbed and were scavenged by predators including Common Ravens, pine martens, coyotes, Bald Eagles, and Red-tailed Hawks.
So, while storms can be devastating to some birds, others might be spared. This particular New Mexico storm may have caught many birds off guard. The unseasonably warm weather that preceded the storm may have resulted in wildlife that remained in marginal habitat, and then been unable to move to a more desirable location. There is evidence; however, that birds can sense changes in barometric pressure, and use this information to determine when to move to a new location. Numerous radar studies of birds migrating over the Gulf of Mexico have shown that birds are able to determine when winds aloft are favorable for northward or southward migration. Preceding storms from the northwest, Sandhill Cranes flocks often remain stationary, feeding voraciously on grains, until shortly before the storm’s arrival when higher, more favorable winds speed them south to a new location. One of the species known to winter on the open expanses of grassland in northern New Mexico is the Lark Bunting. There is evidence that buntings on the eastern plains of New Mexico also can predict weather, and leave prior to the onset of major storms. The week following the storm, the sky was blackened by thousands of buntings that suddenly appeared on the Armendaris Ranch in the Journada del Muerto, a phenomenon not previously reported in this south-central New Mexico location.

Studies by researcher, Bob Gill, from Anchorage, Alaska, support this theory. Gill attached radio transmitters to Bristle-thighed Curlews. These Arctic nesting shorebirds traditionally fly non-stop over the Pacific Ocean to the French Mariana Islands. The birds wait at staging areas until intuitive knowledge of high pressure from west or east, enables them to determine favorable winds that increase their chances of successful flight. With favorable winds, the curlews can fly the non-stop distance in 3-4 days. One transmittered curlew, started south, then circled around, and returned north. When favorable winds appeared near Tahiti, this intrepid bird overflew its destination before correcting its direction and landing at its traditional wintering site at French Mariana islands, after flying non-stop for 8 days.

Dry feathers are very nearly the best the insulation provided in nature. In cold weather, juncos, sparrows, finches, and other ground feeding birds frequently drop down to the ground, covering their legs and feet with their breast feathers while pausing in their search for food. All birds have the ability to enhance their insulation by fluffing out their feathers to increase the thickness of their coat. However, wet feathers provide little or no insulation, and the unfortunate individuals that are unable to stay dry almost certainly succumb to hypothermia.

Like livestock and wild mammals, the greatest threat to birds during a winter storm event is the inability to find sufficient food supplies. Logically, large animals can survive for longer periods without food and water than small ones, and this is true for birds as well. A time/activity budget study conducted on Baird’s Sparrow, a small grassland dwelling bird, has shown that this species needs one seed every 8-10 seconds to survive, essentially eating throughout the daylight hours. Heavy, wet snow blanketing and crushing fragile grasses and forbs for several days or weeks, prevent small songbirds from reaching vital food sources. Similarly, lack of water, in the frozen aftermath of a storm, can be devastating to birds and other wildlife. Some birds, like the American Robin, have been observed eating snow to obtain moisture following storms.

So, what can you, the compassionate birder do, to aid your feathered friends in situations like this? This is the time to be particularly generous with the seed, suet, and water you provide in your back yard. The extra food you provide may mean the difference between life and death to the birds that flock to feeders following a storm. Large seeds, like black oil sunflower that is high in fat content and has a relatively thin shell, can be easily hulled by small birds. Sunflower seed can be tossed onto the sidewalks and other icy areas where it, combined with the actions of foraging songbirds, help to break down the ice and snow. Rather than purchasing suet cakes, why not try making your own suet! Birds love it, and you can add a wide array of nutritious tidbits, from shelled peanuts to raisins. And, of course, break the ice crust from the top of your bird bath, and fill with fresh water daily, or add a bird bath heater to keep it from freezing in the first place.

No-melt Peanut Butter Suet Recipe

1 cup crunch peanut butter
2 cups quick cooking oatmeal
2 cups corn meal
1 cup lard (no substitutions)
1 cup white flour
1/3 cup sugar

Optional additions: raw shelled peanuts, raisins, cranberries, dried fruit. Be creative!

Melt the lard and the peanut butter, then stir in the remaining ingredients. Line a 9 x 13 cake pan with waxed paper (to ease removal), and pour the mixture into the pan. Refrigerate until cooled. Cut into cakes and store in the freezer.

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