Karie L. Decker

Nest predation, food, and female age explain seasonal declines in clutch size

The selection pressures responsible for intra- and interspecific variation in avian clutch size have been debated for over half a century. Seasonal declines in clutch size represent one of the most robust patterns in avian systems, yet despite extensive research on the subject, the mechanisms underlying this pattern remain largely unknown. We tested a combination of experimental and observational predictions to evaluate ten hypotheses, representing both evolutionary and proximate mechanisms proposed to explain seasonal declines in avian clutch size. In line with long held life-history theory, we found strong support for both an evolved and proximate response to food availability for young. We also found evidence consistent with predictions that proximate level experiential nest predation influences seasonal declines in clutch size. Finally, older females appear to invest more in reproduction (initiate nests earlier and lay larger clutches) and choose better territories than younger females. Our results highlight the importance of examining multiple hypotheses in a theoretical context to elucidate the ecological processes underlying commonly observed patterns in life history.

Effects of an Unseasonable Snowstorm on Red-Faced Warbler Nesting Success

Abstract. Earlier initiation of nests by breeding birds may reflect an adaptive response to changes in food availability or warming of spring temperatures, but the consequences of initiating nests too early may be severe, particularly at high elevations. A rare snowstorm in late May 2008 resulted in nest abandonment by 68% of Red-faced Warblers (Cardellina rubrifrons) breeding in a high-elevation riparian ecosystem of southeastern Arizona. In addition, climate data from our study site from 1950 to 2008 revealed higher-than-average springtime temperatures during the past 10 years. If birds respond to this increase in springtime temperatures by nesting earlier their vulnerability to spring snowstorms may increase.

Natural history and breeding biology of the Rusty-breasted Antpitta (Grallaricula ferrugineipectus)

Abstract We provide substantial new information on the breeding biology of the Rusty-breasted Antpitta (Grallaricula ferrugineipectus ferrugineipectus) from 40 nests during four consecutive breeding seasons at Yacambú National Park in Venezuela. Vocalizations are quite variable in G. ferrugineipectus. Nesting activity peaked in April when laying began for half of all nests monitored. The date of nest initiation pattern suggests this species is single-brooded. Both parents incubate and the percent of time they incubate is high (87–99%) throughout the incubation period. The incubation period averaged (± SE) 17.0 ± 0.12 days, while the nestling period averaged 13.37 ± 0.37 days. G. f. ferrugineipectus has the shortest developmental time described for its genus. Time spent brooding nestlings decreased as nestlings grew, but was still greater at pin feather break day than observed in north temperate species. The growth rate constant based on mass (k = 0.41) and tarsus length (k = 0.24) was lower than the k for north temperate species of similar adult mass. All nesting mortality was caused by predation and overall daily survival rate (± SE) was relatively low (0.94 ± 0.01) yielding an estimated 15% nest success.

Translating statistical species-habitat models to interactive decision support tools

Understanding species-habitat relationships is vital to successful conservation, but the tools used to communicate species-habitat relationships are often poorly suited to the information needs of conservation practitioners. Here we present a novel method for translating a statistical species-habitat model, a regression analysis relating ring-necked pheasant abundance to landcover, into an interactive online tool. The Pheasant Habitat Simulator combines the analytical power of the R programming environment with the user-friendly Shiny web interface to create an online platform in which wildlife professionals can explore the effects of variation in local landcover on relative pheasant habitat suitability within spatial scales relevant to individual wildlife managers. Our tool allows users to virtually manipulate the landcover composition of a simulated space to explore how changes in landcover may affect pheasant relative habitat suitability, and guides users through the economic tradeoffs of landscape changes. We offer suggestions for development of similar interactive applications and demonstrate their potential as innovative science delivery tools for diverse professional and public audiences.