Handbook for managing canada geese and cackling geese in southern Canada: chapter 1
Understanding Canada Geese | Biology of Canada Geese
3. Understanding Canada Geese
Prior to the late 1960s, the Canada Goose was considered a migrant and temporary visitor in southern Canada. Beginning in the 1970s, Canada Goose populations were restored, or in some cases introduced, in several areas of southern Canada to provide a population for both local hunting and wildlife viewing. Since the 1970s, however, these temperate-breeding Canada Geese have flourished in the human modified landscapes of southern Canada and their numbers have increased substantially. They have been so successful because the current landscape provides them with everything they need. Modern agriculture provides them with a virtually unlimited year-round supply of high quality food; shoreline development that replaces forest with lawns provides food for goslings with the safety of water close by; and increasing urban/suburban development provides protection from both natural predators and human hunters.
In the Lower Fraser Valley of British Columbia, for example, the number of Canada Geese reported in the 1995 Christmas Bird Count was 50 times higher than the number reported in the 1965 Christmas Bird Count. In southern Ontario, the temperate-breeding population has increased from about 2000 in the early 1970s to nearly half a million in 2008. Rapid population growth of temperate-breeding geese has also occurred in prairie Canada, in southwestern Quebec and New Brunswick. This phenomenon is not unique to Canada; rather, it has occurred steadily over the last 30 to 50 years in settled areas across the temperate zone of North America. Northern-breeding populations of Canada Geese have also benefited from large-scale transformation of the landscape from forest to annual crops. In fact, the enormous amounts of food now available on agricultural lands, which increases both overwinter survival and reproductive output, have allowed many North American populations of geese to attain historically high levels.
Most populations of Canada Geese breed in remote northern areas and fly south to overwinter; they are present in southern Canada only in spring and fall. These geese are commonly referred to as migratory. However, Canada Geese are now year-round residents in several areas and these are commonly referred to as ‘’resident’’ geese. While some of these geese may indeed spend the entire year in southern Canada, many of them also head south for at least short periods during the harshest part of the winter. Contrary to popular belief, these so-called resident Canada Geese are not migratory geese that stopped migrating; they are simply the result of increasing local breeding populations that have become established either from reintroductions or natural population growth. Because, young geese tend to return to nest where they were raised and migration behaviour is learned from their parents, with each generation these temperate-breeding populations continue to grow.
4. Biology of Canada Geese
Canada Geese are herbivores. In natural areas, their foods include grass and other tender plants, seeds and berries, as well as aquatic vegetation. In agricultural areas, they eat grasses, cultivated grains and some vegetable crops. In fall and winter, geese consume large quantities of grains which provide energy and help build fat reserves; however, in summer growing goslings and moulting adult geese require the higher levels of protein found in young shoots of grass. Because taller, older grasses are coarser and offer less nutritional value, geese prefer new grass shoots, which explains their preference for mowed lawns. In spring, migrating geese may also build protein reserves by consuming young shoots of corn and other cereal crops, spring-planted pasture, and early legumes.
4.2 Importance of Water
Although geese mostly feed on land, they usually nest near water and prefer secluded areas. Water is used for drinking, preening and bathing, and is the best avenue of escape when flightless young and moulting adult geese are threatened. Nests are usually located at the water's edge or a short distance from the shoreline, and a nest surrounded by water offers excellent protection from land-based predators. Islands in wetlands are thus prime nesting sites and may accommodate high densities of nests. When goslings are young and adults are flightless, geese rarely stray far from water. After their goslings have begun flying and throughout the rest of the year, geese forage during the day on grass or crops, but generally return to large bodies of water to roost at night.
Timing of nesting may vary by region, depending upon the local climate. In southwestern British Columbia and southern Ontario where large populations of temperate-breeding Canada Geese occur, geese pair up and establish territories by early to mid-March. In prairie Canada, nesting usually begins in early April. Northern-breeding populations nest later, depending upon when spring conditions arrive in their breeding area. Nesting pairs tend to use the same area year after year. First-time breeders (two to three years old) generally nest near where they first learned to fly. The nest is usually a roughly woven collection of grasses and other vegetation and can be up to a metre in diameter. Canada Geese are remarkably adaptable in choosing nest sites. Natural nesting habitat includes marshes, islands, cliffs and trees; however, Canada Geese have also been reported to nest on barges, pilings, apartment balconies, in flower boxes and rooftop gardens.
4.4 Egg Laying and Brood Rearing
Laying a complete clutch of eggs takes a little more than a week. In temperate-breeding populations, the first pairs may begin egg-laying by the end of March and the last will complete their clutches by the end of April, but laying can continue into late May. Mild weather in some years may allow geese to nest as early as February. An average nest contains 5 or 6 eggs, but some may contain 10 or more eggs. Incubation lasts about 25 days, with peak hatch occurring in early to mid-May. The goslings of a goose family are collectively known as a brood. The brood-rearing period, the time from hatch until young geese are able to fly, lasts about two months.
Once a year, geese must grow new wing feathers, a process called moulting, which leaves the geese unable to fly for several weeks. Moult occurs between mid-May/early June and late July. Most birds are in moult by mid-June. During this period, adult geese will be flightless for four to six weeks. When flightless, geese are particularly vulnerable to predation and will seek refuge in safe areas. Non-breeding birds often gather in large moulting flocks at this time. Breeding birds that successfully hatched goslings will stay near their nesting areas to moult while rearing their young. They regain the ability to fly at about the same time as their young begin flying. Once this happens, young and adult geese move throughout urban, suburban and nearby agricultural areas, feeding to build fat reserves in preparation for winter.
Northern-breeding Canada and Cackling Geese nest in arctic and sub-arctic regions and overwinter mainly in the United States. During both spring and fall migration, they pass through southern Canada, spending several weeks feeding to build reserves. Migrating geese are present in spring beginning in late March and usually depart for northern breeding areas sometime in April. In spring, they may forage on young shoots of newly seeded crops. In the fall, they usually begin arriving in southern Canada in late September and may stay around until freeze up. During this time, they feed mainly on waste grains. Generally, by the time migrant geese arrive in the fall, most crops have been harvested and they may feed on agricultural lands without causing problems. Also, they are hunted in the fall so there are fewer conflicts than in spring. Temperate-breeding geese do not undertake regular annual long-distance migration like their northern-breeding cousins, but individuals not yet of breeding age often migrate north several hundred kilometres or more to moult, and flocks may head south in winter if conditions are harsh making open water and food unavailable.
4.7 Population Growth and Limiting Factors
The abundant supply of food provided by modern agriculture has allowed most North American goose populations to flourish and reach high population levels. Before this virtually limitless supply of food was available, population growth was controlled to some extent by poor over-winter survival or lack of sufficient nutrient reserves to devote to laying eggs during the breeding season. Northern-breeding Canada and Cackling Geese still face a more unpredictable climate than temperate-breeders so their breeding success is more variable year to year and most of these populations tend to be relatively stable. Adverse weather is less of a limiting factor for temperate-breeders; they are more likely to lay full clutches of eggs and successfully hatch them year after year. This consistent production of young every year results in rapidly growing populations. Losses of adults, eggs and young from predators are also often lower in temperate-breeding geese, particularly in urban areas.
One of the most important limiting factors for goose population growth is the survival rate of adult geese. Geese typically begin breeding at 2-3 years of age and adults can live for 20 years or more. Each year they nest and, if successful, produce a new batch of young; after 20 years the number of young produced by one pair can be staggering. Hunting is the most important source of mortality for adult geese. Because of this, population size can be managed to some extent by changing hunting regulations to increase harvest. One of the reasons urban populations tend to grow quickly is because geese living in cities do not face as much hunting pressure as do their rural or migratory counterparts. Hunting of geese has been restricted in recent years, with the closure of areas previously open to hunting and the introduction of municipal bylaws prohibiting the discharge of firearms in urban and suburban areas, and this has contributed significantly to population growth.
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