Augmenting wild populations and food resources

NEGRO, J.J.; SARASOLA, J.H.; BARCLAY, J.H.

Raptor Research and Management Techniques

Hancock House Publishers

Lugar: Blaine, WA, USA; Año: 2007; p. 399 - 408

Many populations of raptors, including several in North America, have substantially declined or exist at levels that merit population augmentation (Stattersfield and Capper 2000; see below). Augmenting wild populationsAugmenting wild populations has been defined as “increasing a population whose numbers have been reduced” (Barclay 1987). We retain that definition and continue to separate population augmentation into (1) techniques that take advantage of a population’s ability to increase by its own reproductive efforts, and (2) those that involve adding individuals from outside of the population. Management programs must be based on an understanding of the life history of the species in question and a thorough assessment of the conservation status of the population. They should include research to identify factors that have contributed to reducing the population, and an evaluation of whether the population is likely to respond favorably to management attempts. What follows is based on the assumption that there is sufficient information about the life history of a species, including its past and present conservation status, to select and employ effective management techniques; and that any critical limiting factors will not nullify input from population- augmentation techniques. Raptors are long-lived species that produce relatively few fledglings when they attempt to breed (Newton 1979). In species with this demographic strategy, adult survival is the life-history trait that contributes most to population growth (Lande 1988). In other words, even small changes in adult survival rates may have a larger impact on the persistence of populations over time than, for example, breeding success (Hiraldo et al. 1996). Keeping in mind that the best strategy to augment a raptor population is to enhance adult survival, we have to acknowledge that this parameter may not be amenable to human alteration, and that productivity can become the only parameter susceptible to improvement. Thus, as this is often the case, we have focused on management techniques aimed at increasing productivity.“increasing a population whose numbers have been reduced” (Barclay 1987). We retain that definition and continue to separate population augmentation into (1) techniques that take advantage of a population’s ability to increase by its own reproductive efforts, and (2) those that involve adding individuals from outside of the population. Management programs must be based on an understanding of the life history of the species in question and a thorough assessment of the conservation status of the population. They should include research to identify factors that have contributed to reducing the population, and an evaluation of whether the population is likely to respond favorably to management attempts. What follows is based on the assumption that there is sufficient information about the life history of a species, including its past and present conservation status, to select and employ effective management techniques; and that any critical limiting factors will not nullify input from population- augmentation techniques. Raptors are long-lived species that produce relatively few fledglings when they attempt to breed (Newton 1979). In species with this demographic strategy, adult survival is the life-history trait that contributes most to population growth (Lande 1988). In other words, even small changes in adult survival rates may have a larger impact on the persistence of populations over time than, for example, breeding success (Hiraldo et al. 1996). Keeping in mind that the best strategy to augment a raptor population is to enhance adult survival, we have to acknowledge that this parameter may not be amenable to human alteration, and that productivity can become the only parameter susceptible to improvement. Thus, as this is often the case, we have focused on management techniques aimed at increasing productivity.(Barclay 1987). We retain that definition and continue to separate population augmentation into (1) techniques that take advantage of a population’s ability to increase by its own reproductive efforts, and (2) those that involve adding individuals from outside of the population. Management programs must be based on an understanding of the life history of the species in question and a thorough assessment of the conservation status of the population. They should include research to identify factors that have contributed to reducing the population, and an evaluation of whether the population is likely to respond favorably to management attempts. What follows is based on the assumption that there is sufficient information about the life history of a species, including its past and present conservation status, to select and employ effective management techniques; and that any critical limiting factors will not nullify input from population- augmentation techniques. Raptors are long-lived species that produce relatively few fledglings when they attempt to breed (Newton 1979). In species with this demographic strategy, adult survival is the life-history trait that contributes most to population growth (Lande 1988). In other words, even small changes in adult survival rates may have a larger impact on the persistence of populations over time than, for example, breeding success (Hiraldo et al. 1996). Keeping in mind that the best strategy to augment a raptor population is to enhance adult survival, we have to acknowledge that this parameter may not be amenable to human alteration, and that productivity can become the only parameter susceptible to improvement. Thus, as this is often the case, we have focused on management techniques aimed at increasing productivity.