Bird abundance still down, says naturalistMonday, April 14, 2014 by: Bob Mihell
After one of the harshest winters in recent memory the diversity of bird species that winter over in our region was “only slightly lower than average”, but the overall abundance or numbers of birds have dropped considerably, says a member of the Sault Naturalists.
Ken McIlwrick is an experienced and active naturalist locally, who leads and participates in several bird counts and programs in Algoma.
He also contributes data to several Internet bird sites, including Journey North, eBird, SaultBirds, and ONTBIRDS.
Interestingly, he said, the decline in the overall number of birds in the area began last fall, before the cold and snow hit Algoma, and continued throughout the winter.
“People who regularly feed birds in the fall and winter would have been quite aware of this.”
McIlwrick added winter mortality among birds occurs commonly because of lack of food, disease, old age, or predation.
He said too some decline in the overall bird population is a result of birds temporarily leaving the area.
The American Goldfinch, for example.
Regarding migrating birds, their return north has not been delayed or hampered as much by the prolonged winter as one would expect, with a few exceptions.
He said the return of some waterfowl species, like the tundra swan, is later than usual.
“But for the most part, birds seem to be returning regardless,” he said. “We even have had some early arrivals, for example, the yellow-rumped warbler and turkey vulture.”
Bird species in Algoma, he pointed out, fall into four distinct categories.
The first group, resident birds like the black-capped chickadee, remain all year but may temporarily move short distances during harsh conditions.
“They can quickly respond to local climate cues, and usually are well-adapted to local weather variations,” he said.
A second group, nomadic species, such as the Pine Siskin, are always on the move, usually in a flock, and will relocate to areas with greater food supply.
Migrating birds fall into two groups: short-distant migrants, and long-distant or neo-tropical migrants.
Short-distant migrants, like Lincoln’s sparrow, overwinter in central or southern U.S. states. These species rely on both solar cues (daylight hours), and climatic cues (temperature, wind speed and direction, and precipitation) during migration.
McIlwrick said when migrating either north or south these species sometimes get “caught off-guard” by unexpected weather, but they are more able to predict what is in “store for them” in Ontario, and time their returns accordingly.
Long-distance migrating species, such as the magnolia warbler, head to Central and South America in winter.
They depend on daylight hours during migration, but can adjust to weather changes as they near their breeding territories.
McIlwrick said what often affects spring mortality in bird species is the supply of food they eat. For birds that feed on flying insects, like flycatchers, warblers, vireos, swallows, and nighthawks, a sudden cold snap can kill off or reduce their source of food and those birds end up dying from exposure.
Similarly, ground feeders can be threatened by snow cover or late snowfalls that limit their food supply.
McIlwrick noted that aerial insectivores (birds whose food source are flying insects) are in decline all across North America.
He agreed too that humans often have ambivalent or mixed attitudes toward the bird population, especially the more common species in urban environments, such as pigeons, crows, gulls, and wrens.
Humans seem to do this with most life forms, whether wildlife or plants, when they are perceived as “nuisances” because of factors like damage to property, gardens, crops, and public areas like beaches and parks, McIlwrick said.
He added, however, that levels of tolerance vary greatly among individuals, and “often comes down to our own personal perceptions, how we were raised, and how influenced we are by public attitudes.”
Some people are strongly opposed to non-indigenous species, either introduced or spread from other continents, because “they tend to be invasive in nature, and often thrive in their new surroundings”, he noted.
Examples include: dandelions, purple loosestrife, emerald ash borers, zebra mussels, rock pigeons, and European starlings.
In some instances, human interaction with bird populations becomes confrontational, and
McIlwrick provided several specific examples.
Airports actively scare, remove or kill birds to keep people safe, and protect their assets from damage or destruction.
Many farmers actively scare or kill birds to protect their crops and livestock, and keep their facilities free from excrement.
Golf courses and city parks actively scare herbivorous birds to protect their turf from foraging damage and excrement accumulation.
Thousands of cormorant and Canada goose eggs have been oiled or shaken in an attempt to reduce their populations.
And the plastic owl, plastic hawk and window silhouette industry has made its mark in every city, he said.
Meanwhile McIlwrick said also that urban expansion and human activities have altered the habitats of bird species and other animals by lowering vegetation, and water resources, for example, by the draining of wetland areas.
“These changes can be pretty dramatic, and result in habitats that generally don’t resemble what was there before, and therefore result in a change in bird species’ composition and abundance,” he said. “If there are not enough natural parks or natural areas in proximity to all this development, then you are left with a bird population that is primarily urban tolerant.”
Ironically, one urban bird dweller, the chimney sweep, a species that used to benefit from large open chimneys in cities, has been forced to seek out more natural roost sites in trees, cliff overhangs, or caves in rural or forested areas, as traditional chimneys disappear.
McIlwrick said that it is common for bird species to move to areas changed by humans, such as farmland or heavily forested areas, if it supports their habitat preferences.
“Habitat change or loss, of course, becomes a major concern when it is the last of that particular habitat left, or the loss or change of a certain habitat will impact on a species at risk,” he stressed. “A proactive approach to habitat management is always better than a reactive approach. I would never discount the impacts that humans have had, but we must remember that bird species have come and gone over the millennia with or without the influence of humanity.”
McIlwrick concluded with this observation: “I think our challenge on this planet is to keep things in perspective, and to remember that every living and non-living entity on this planet is connected in some way. The more that people learn about their surroundings, the more they tend to participate in the care of them.”