Search

Search Results

• 1. [Article] Nest Reuse by Eastern Kingbirds: Adaptive Behavior or Ecological Constraint?

  The reuse of old nests by open-cup nesting passerines is a seemingly rare but potentially adaptive behavior if, as a consequence, females begin to breed earlier, lay larger clutches, or fledge more young. ...

  Citation × Citation Citation Abstract Copy Title: Nest Reuse by Eastern Kingbirds: Adaptive Behavior or Ecological Constraint? Author: Redmond, Lucas J., Murphy, Michael T., Dolan, Amy C. Year: 2007 The reuse of old nests by open-cup nesting passerines is a seemingly rare but potentially adaptive behavior if, as a consequence, females begin to breed earlier, lay larger clutches, or fledge more young. We report an unusually high rate of nest reuse (~10% of 341 nests) for Eastern Kingbirds (Tyrannus tyrannus) breeding at Malheur National Wildlife Refuge, Oregon. We found no difference in availability of nesting habitat or food abundance in territories in which nests were and were not reused. We also found no support for the hypotheses that kingbirds benefited from nest reuse by breeding earlier, laying larger clutches, or fledging more young, and, contrary to expectations, females that reused nests laid significantly smaller eggs than females who built their own nests. Nest reuse was independent of age: a roughly equal number of females for which we had multiple years of data both reused nests and built new nests, but at different points in their lives. Competition for nest sites seems high at Malheur National Wildlife Refuge because many open-cup nesting species utilize similar nest sites in the limited zone of riparian vegetation. A shortage of high-quality nest sites, coupled with interspecific competition, may underlie the high frequency of nest reuse in this kingbird population. Title: Nest Reuse by Eastern Kingbirds: Adaptive Behavior or Ecological Constraint? Author: Redmond, Lucas J., Murphy, Michael T., Dolan, Amy C. Year: 2007 The reuse of old nests by open-cup nesting passerines is a seemingly rare but potentially adaptive behavior if, as a consequence, females begin to breed earlier, lay larger clutches, or fledge more young. We report an unusually high rate of nest reuse (~10% of 341 nests) for Eastern Kingbirds (Tyrannus tyrannus) breeding at Malheur National Wildlife Refuge, Oregon. We found no difference in availability of nesting habitat or food abundance in territories in which nests were and were not reused. We also found no support for the hypotheses that kingbirds benefited from nest reuse by breeding earlier, laying larger clutches, or fledging more young, and, contrary to expectations, females that reused nests laid significantly smaller eggs than females who built their own nests. Nest reuse was independent of age: a roughly equal number of females for which we had multiple years of data both reused nests and built new nests, but at different points in their lives. Competition for nest sites seems high at Malheur National Wildlife Refuge because many open-cup nesting species utilize similar nest sites in the limited zone of riparian vegetation. A shortage of high-quality nest sites, coupled with interspecific competition, may underlie the high frequency of nest reuse in this kingbird population. Close

• 2. [Article] Experimental Analysis of Nest-Site Choice and its Relationship to Nest Success in an Open-Cup–Nesting Passerine

  Nest placement presumably reflects selection for secure sites to minimize failure. Most tests of this hypothesis, however, have failed to support it. We used artificial nests (ARTs) to experimentally evaluate ...

  Citation × Citation Citation Abstract Copy Title: Experimental Analysis of Nest-Site Choice and its Relationship to Nest Success in an Open-Cup–Nesting Passerine Author: Cancellieri, Sarah, Murphy, Michael T. Year: 2014 Nest placement presumably reflects selection for secure sites to minimize failure. Most tests of this hypothesis, however, have failed to support it. We used artificial nests (ARTs) to experimentally evaluate nest-site-choice behavior by an open-cup–nesting bird, the Eastern Kingbird (Tyrannus tyrannus). In 2010 and 2011, we placed ARTs in trees in the riparian zone at Malheur National Wildlife Refuge, Oregon, USA, to test whether (1) characteristics describing the physical location in trees of used and unused ARTs differed, (2) used ART sites more closely resembled naturally chosen sites, (3) successful natural nests (NATs) and successful ARTs were similarly located along the major axis describing nest placement, and (4) unused ARTs resembled failed NATs. Used and unused ART sites differed, but unused ART sites were more similar to NAT sites. The latter unexpected result occurred because (1) unused ARTs were located at sites between more heavily used higher and lower locations and (2) most kingbirds nesting at lower locations used ARTs instead of building their own nest. In both ARTs and NATs, differences between successful and failed nests exhibited the same pattern for most nest-site variables, and the major gradient describing nest location was the same; successful nests tended to be placed on more vertically oriented branches that were placed closer to the top of the tree. Kingbird nest placement was thus selective. However, extensive overlap in the locations in trees of failed NATs and both successful and unused ARTs suggests that other factors, such as macrohabitat characteristics or prior experience of individual birds with particular nest sites, may have influenced success and/or decisions to use or reject nests in particular locations. Thus, consideration of phenomena beyond the nest site itself may be required to fully understand the process of nest-site choice in birds. Title: Experimental Analysis of Nest-Site Choice and its Relationship to Nest Success in an Open-Cup–Nesting Passerine Author: Cancellieri, Sarah, Murphy, Michael T. Year: 2014 Nest placement presumably reflects selection for secure sites to minimize failure. Most tests of this hypothesis, however, have failed to support it. We used artificial nests (ARTs) to experimentally evaluate nest-site-choice behavior by an open-cup–nesting bird, the Eastern Kingbird (Tyrannus tyrannus). In 2010 and 2011, we placed ARTs in trees in the riparian zone at Malheur National Wildlife Refuge, Oregon, USA, to test whether (1) characteristics describing the physical location in trees of used and unused ARTs differed, (2) used ART sites more closely resembled naturally chosen sites, (3) successful natural nests (NATs) and successful ARTs were similarly located along the major axis describing nest placement, and (4) unused ARTs resembled failed NATs. Used and unused ART sites differed, but unused ART sites were more similar to NAT sites. The latter unexpected result occurred because (1) unused ARTs were located at sites between more heavily used higher and lower locations and (2) most kingbirds nesting at lower locations used ARTs instead of building their own nest. In both ARTs and NATs, differences between successful and failed nests exhibited the same pattern for most nest-site variables, and the major gradient describing nest location was the same; successful nests tended to be placed on more vertically oriented branches that were placed closer to the top of the tree. Kingbird nest placement was thus selective. However, extensive overlap in the locations in trees of failed NATs and both successful and unused ARTs suggests that other factors, such as macrohabitat characteristics or prior experience of individual birds with particular nest sites, may have influenced success and/or decisions to use or reject nests in particular locations. Thus, consideration of phenomena beyond the nest site itself may be required to fully understand the process of nest-site choice in birds. Close

• 3. [Article] Demography of a Ground Nesting Bird in an Urban System: Are Populations Self-Sustaining?

  Urbanization poses threats to earth’s biota, and retention of remnant native habitat in protected areas within expanding urban boundaries may help alleviate threats to wildlife. However, it is unclear ...

  Citation × Citation Citation Abstract Copy Title: Demography of a Ground Nesting Bird in an Urban System: Are Populations Self-Sustaining? Author: Bartos Smith, Sarah, McKay, Jenny E., Richardson, Jennifer K., Shipley, Amy A., Murphy, Michael T. Year: 2016 Urbanization poses threats to earth’s biota, and retention of remnant native habitat in protected areas within expanding urban boundaries may help alleviate threats to wildlife. However, it is unclear for nearly all nonsynanthropic (i.e., not benefiting from an association with humans) species whether vital rates in urban habitats can sustain populations or if populations persist only through immigration from outside the urban boundary. We conducted a three-year study of spotted towhees (Aves: Pipilo maculatus) breeding in four undeveloped parks in Portland, OR, USA, to measure park-specific seasonal reproductive output (F) and annual adult survival (SA). We developed a stochastic model that combined F and SA with an estimate of first-year survival to measure population growth rate (λ) in all parks assumed to be closed to immigration. F differed among parks but SA did not. Relatively high F was possible because many pairs raised >1 brood/season. When combined with empirical estimates of survival through the 30-day period of post-fledging parental care (SD = 0.645), only 2 of 4 parks were self-sustaining (i.e., λ > 1.0). However, SD reflected substantial loss of fledglings to domestic cats (Felis catus). Assuming no loss to cats and either partial compensatory or additive mortality of fledglings substantially improved prospects of population persistence for declining (sink) populations. Moreover, allowing low levels of immigration to sinks reversed population declines in most parks even when vital rates were insufficient to maintain populations. Our results suggest that nonsynanthropic bird species can persist in urban landscapes, but also that offspring mortality in the post-fledging period may be a critical determinant of population viability. Title: Demography of a Ground Nesting Bird in an Urban System: Are Populations Self-Sustaining? Author: Bartos Smith, Sarah, McKay, Jenny E., Richardson, Jennifer K., Shipley, Amy A., Murphy, Michael T. Year: 2016 Urbanization poses threats to earth’s biota, and retention of remnant native habitat in protected areas within expanding urban boundaries may help alleviate threats to wildlife. However, it is unclear for nearly all nonsynanthropic (i.e., not benefiting from an association with humans) species whether vital rates in urban habitats can sustain populations or if populations persist only through immigration from outside the urban boundary. We conducted a three-year study of spotted towhees (Aves: Pipilo maculatus) breeding in four undeveloped parks in Portland, OR, USA, to measure park-specific seasonal reproductive output (F) and annual adult survival (SA). We developed a stochastic model that combined F and SA with an estimate of first-year survival to measure population growth rate (λ) in all parks assumed to be closed to immigration. F differed among parks but SA did not. Relatively high F was possible because many pairs raised >1 brood/season. When combined with empirical estimates of survival through the 30-day period of post-fledging parental care (SD = 0.645), only 2 of 4 parks were self-sustaining (i.e., λ > 1.0). However, SD reflected substantial loss of fledglings to domestic cats (Felis catus). Assuming no loss to cats and either partial compensatory or additive mortality of fledglings substantially improved prospects of population persistence for declining (sink) populations. Moreover, allowing low levels of immigration to sinks reversed population declines in most parks even when vital rates were insufficient to maintain populations. Our results suggest that nonsynanthropic bird species can persist in urban landscapes, but also that offspring mortality in the post-fledging period may be a critical determinant of population viability. Close