Drivers of Flight Performance of California Condors (Gymnogyps californianus)

ABSTRACT Flight behavior of soaring birds depends on a complex array of physiological, social, demographic, and environmental factors. California Condors (Gymnogyps californianus) rely on thermal and orographic updrafts to subsidize extended bouts of soaring flight, and their soaring flight performance is expected to vary in response to environmental variation and, potentially, with experience. We collected 6298 flight tracks described by high-frequency GPS telemetry data from five birds ranging in age from 1 to 19 yr old and followed over 32 d in summer 2016. Using these data, we tested the hypothesis that climb rate, an indicator of flight performance, would be related to the topographic and meteorological variables the bird experienced, and also to its age. Climb rate was greater when condors were flying in faster winds and during environmental conditions that were conducive to updraft development. However, we found no effect of age on climb rate. Although many of these relationships were expected based on flight theory, the lack of an effect of age was unexpected. Our work expands understanding of the relationship condors have with the environment, and it also suggests the potential for as-yet unexplored complexity to this relationship. As such, this study provides insight into avian flight behavior and, because flight performance influences bird behavior and exposure to anthropogenic risk, it has potential consequences for development of conservation management plans.

Mortality among free-ranging California condors (Gymnogyps californianus) during 2010–2014 with determination of last meal and toxicant exposure

Over the past 30 years, the California condor (Gymnogyps californianus) population has rebounded from 22 individuals to over 200 birds living in the wild. Historical impacts to the population have been largely anthropogenic. In this study, we explore mortality and cause of death data from condors that died during the years 2010-2014 and compare these to mortality data described by Rideout et al. in 2012, covering the years 1992-2009. In addition, morphologic and genetic analysis of the contents of the upper gastrointestinal (GI) tract was performed on the 2010-2014 condor mortalities to determine animal origins of the last meal eaten. The maximum population at risk within this time frame was 329 birds. During this time, 88 condors died and underwent post-mortem examination, and 41 birds were lost to tracking efforts and presumed dead (crude mortality rate of 39%; 129/329). A cause of death was determined for 66 of the 88 necropsied birds. Lead toxicosis remained a significant negative factor in condor population recovery, being related to the deaths of 37 adult and juvenile condors (proportional mortality rate 56%). Compared to condors succumbing to other causes of death, cattle were less often part of the last meal of lead-intoxicated condors. Based on these data, continued efforts to mitigate the impact of lead on California condors should be pursued.

The endangered California Condor (Gymnogyps californianus) population is exposed to local haemosporidian parasites

The endangered California Condor (Gymnogyps californianus) is the largest New World Vulture in North America. Despite recovery program success in saving the species from extinction, condors remain compromised by lead poisoning and limited genetic diversity. The latter makes this species especially vulnerable to infectious diseases. Thus, taking advantage of the program of blood lead testing in Arizona, condor blood samples from 2008 to 2018 were screened for haemosporidian parasites using a nested polymerase chain reaction (PCR) protocol that targets the parasite mitochondrial cytochrome b gene. Plasmodium homopolare (Family Plasmodiidae, Order Haemosporida, Phylum Apicomplexa), was detected in condors captured in 2014 and 2017. This is the first report of a haemosporidian species infecting California Condors, and the first evidence of P. homopolare circulating in the Condor population from Arizona. Although no evidence of pathogenicity of P. homopolare in Condors was found, this study showed that the California Condors from Arizona are exposed to haemosporidian parasites that likely are spilling over from other local bird species. Thus, active surveillance should be an essential part of conservation efforts to mitigate the impact of infectious diseases, an increasingly recognized cause of global wildlife extinctions worldwide, particularly in avian populations considered vulnerable or endangered.