Cruz, J., S. Windels, W.E. Thogmartin, S.M. Crimmins, and B. Zuckerberg. 2023. Survival of Common Loon chicks appears unaffected by Bald Eagle recovery in northern Minnesota. Avian Ecolgoy and Conservation 18(1):7. https://doi.org/10.5751/ACE-02395-180107
Abstract
Recovering species are not returning to the same environments or communities from which they disappeared. Conservation
researchers and practitioners are thus faced with additional challenges in ensuring species resilience in these rapidly changing ecosystems.
Assessing the resilience of species in these novel systems can still be guided by species’ ecology, including knowledge of their population
size, life history traits, and behavioral adaptations, as well as the type, strength, and number of ways that they interact with other species
in the community. We summarized broad trends of Common Loons (Gavia immer) breeding at Voyageurs National Park from 1973 to
2009, and evaluated the effects of increased risk from recovering Bald Eagles (Haliaeetus leucocephalus) on chick survival from 2004
to 2006. Adult Common Loons appear to have increased over time. Using Bayesian survival models that accounted for imperfect
detection of unmarked individuals, we determined that chick survival of Common Loons was high from year to year and was unrelated
to predation risk from Bald Eagles because chicks in territories closer to active nests did not experience greater mortality than those
farther away. We suggest that Common Loon chicks were unaffected by the recovery of this top predator during the three years of
sampling. Previous research indicates that Bald Eagles and other predators are an important source of egg losses, but Common Loons
can compensate by re-nesting. Despite current uncertainties from anthropogenic threats, knowledge of a species’ ecology remains
instrumental in determining its resilience during recovery.
researchers and practitioners are thus faced with additional challenges in ensuring species resilience in these rapidly changing ecosystems.
Assessing the resilience of species in these novel systems can still be guided by species’ ecology, including knowledge of their population
size, life history traits, and behavioral adaptations, as well as the type, strength, and number of ways that they interact with other species
in the community. We summarized broad trends of Common Loons (Gavia immer) breeding at Voyageurs National Park from 1973 to
2009, and evaluated the effects of increased risk from recovering Bald Eagles (Haliaeetus leucocephalus) on chick survival from 2004
to 2006. Adult Common Loons appear to have increased over time. Using Bayesian survival models that accounted for imperfect
detection of unmarked individuals, we determined that chick survival of Common Loons was high from year to year and was unrelated
to predation risk from Bald Eagles because chicks in territories closer to active nests did not experience greater mortality than those
farther away. We suggest that Common Loon chicks were unaffected by the recovery of this top predator during the three years of
sampling. Previous research indicates that Bald Eagles and other predators are an important source of egg losses, but Common Loons
can compensate by re-nesting. Despite current uncertainties from anthropogenic threats, knowledge of a species’ ecology remains
instrumental in determining its resilience during recovery.