Sprague's Pipit
Limiting Factors
A variety of factors may be responsible for the recent declines in continental and provincial populations of the Sprague's Pipit. Although climatic factors, such as
drought, have been shown to decrease local populations of this species, the following discussion focuses on factors with an anthropogenic origin, which may be reversed through appropriate management or conservation
activities. These include
Loss of Native Prairie, Cattle
Grazing, Burning, and Haying.
Loss of Native Prairie:
Native prairie and parkland has been extensively modified by agricultural activities over the past century. Approximately 75% of the Canadian prairies has been converted to agricultural use, including 68% in Alberta. Losses or
)
modifications in the aspen parkland have been even greater, with 80% of these
habitats across the prairie now under agricultural use. In Alberta, only two to 10% of native parkland remains intact. The strong preference of Sprague's Pipits for native grasslands, coupled with extensive loss or modification of these habitats across the Canadian prairies, is undoubtedly a major factor in the rapid decline of Sprague's Pipits in this area. Changes to habitat on the prairies may be most important to this decline, as breeding populations in this region are traditionally much larger than in the parkland.
Cattle Grazing:
Accounts from the Canadian prairies show that Sprague's Pipits prefer ungrazed to moderately-grazed native range, and will decline markedly under more intense grazing pressure. Light to moderate levels of grazing can produce suitable habitat is some regions. This may also be true in some parts of the Canadian prairies and parkland, where Sprague's Pipits prefer intermediate grass height and litter depths. However, grasslands in southern Alberta tend to be more arid, and productivity of grass lower, than in other areas within the range of the Sprague's Pipit. In these areas, moderate levels of grazing are more likely to be detrimental to Sprague's Pipit populations.
Grazing not only modifies habitat suitability for grassland birds, but can reduce reproductive success through behavioral disturbance of nesting birds and trampling of nests by cattle. These factors have not specifically been investigated for Sprague's Pipits, but grazing of suitable habitat at critical phases of the nesting cycle undoubtedly affects recruitment in some areas.
Burning:
In the short term, fire has adverse effects on the abundance of Sprague's Pipits. Density dropped from 0.3 to 0.14
)
pairs/hectare one year after burning in Saskatchewan, but returned to pre-burn levels after three years. Other studies, however, have suggested that burning has longer-term benefits for Sprague's Pipits. Thus, fire may reduce habitat suitability for a brief period, but larger populations for several years thereafter should more than offset initial declines. Sprague's Pipits, and other grassland species that have evolved with frequent fires on the prairies, may therefore be limited by reduced fire frequencies that have accompanied human settlement, and which allow encroachment of shrubs and excessive accumulation of litter.
Haying: Haying, like grazing, alters habitat structure and can have major impacts on habitat for Sprague's Pipits. Furthermore, mowing during the nesting season can cause substantial reproductive failure in grassland birds, including Sprague's Pipits. However, there is only limited information on the responses of Sprague's Pipits to haying of native grasslands, probably because such land use, compared to grazing, is of relatively minor occurrence on the Great Plains.
It is unclear whether haying produces the longer-term benefits that are observed following burning, although it is believed that Sprague's Pipits should
respond well to occasional haying.