Laird A. Henkel

Shorebird Use of Sandy Beaches in Central California

Abstract In this study, the relationship between physical attributes of sandy beaches, levels of human disturbance, and shorebird occurrence was investigated. The linear density km-1 of shorebirds on 42 km of sandy beaches in Monterey Bay, California was documented from late autumn through spring, and the relationship of shorebird densities to two physical variables (slope of beach swash zone, total beach width), one spatial variable (distance to Elkhorn Slough, a wetland of regional importance for shorebirds), and relative level of human disturbance was analyzed using stepwise multiple regression. The six most abundant species were Sanderling (Calidris alba), Willet (Tringa semipalmata), Marbled Godwit (Limosa fedoa), Black-bellied Plover (Pluvialis squatarola), Whimbrel (Numenius phaeopus) and Snowy Plover (Charadrius alexandrinus). Mean abundance of four of the six most abundant species (Marbled Godwit, Willet, Whimbrel, Black-bellied Plover) was negatively related to swash zone slope; flatter beaches supported more shorebirds. Mean abundance of all species analyzed was negatively related to distance to Elkhorn Slough; beaches closer to the mouth of Elkhorn Slough supported more shorebirds. Total beach width had no effect on shorebird occurrence, and level of human use appeared to have no effect. Most shorebird species were more abundant on beaches at low than at high tide, indicating that sandy beaches provide important foraging habitat regionally.

Chronic oiling of marine birds in California by natural petroleum seeps, shipwrecks, and other sources

We assessed temporal and spatial patterns of chronic oiling of seabirds in California during 2005-2010, using data on: (1) live oiled birds reported to the Oiled Wildlife Care Network (OWCN) from throughout the state, and (2) dead oiled birds found during systematic monthly beached-bird surveys in central California. A mean of 245 (± 141 SD) live miscellaneous oiled birds (not associated with known oil spills) were reported to the OWCN per year, and 0.1 oiled dead birds km(-1) per month were found on beach surveys in central California. Chemical fingerprinting of oiled feathers from a subset of these birds (n=101) indicated that 89% of samples tested were likely from natural petroleum seeps off southern and central California. There was a pronounced peak during late winter in the number of oiled birds reported in southern California, which we theorize may be related to large storm waves disturbing underwater seeps.

Effects of Rapid Flight-Feather Molt on Postbreeding Dispersal in a Pursuit-Diving Seabird

Abstract Breeding seabirds have been well studied but seabird ecology during the nonbreeding season is poorly understood because many species disperse far from breeding colonies to molt at sea. We characterized the timing of prebasic molt and postbreeding dispersal, described postbreeding dispersal movements, and estimated changes in body mass during molt for Marbled Murrelets (Brachyramphus marmoratus; Alcidae) in central California, 1999–2004. According to mark–recapture and at-sea surveys, 248–315 of 496–637 individuals (43–50%) used Año Nuevo Bay, located immediately adjacent to nesting areas, for their prebasic molt in August–October. Long-distance dispersal (≥ 100 km) from Año Nuevo Bay by radiomarked Marbled Murrelets was low during breeding (9–13%, n = 46), but was greater for individuals radiomarked at the end of the breeding season (69–90%, n = 20). The mean dispersal dates were 18 May and 21 October for the breeding and postbreeding samples, respectively, and postbreeding dispersal occurred an average of two weeks after molt completion. Mean dispersal distances were 184 km and 256 km in the breeding and postbreeding periods, respectively. Of 12 long-distance dispersers, all moved south except one. Marbled Murrelets gained mass during molt (n = 184), except during a moderate El Niño event in 2002 when mass remained constant. However, birds did not take longer to molt in 2002, which suggests that individuals allocated more energy reserves to molt processes in that year. Apparently, sufficient prey resources were available in Año Nuevo Bay for both basic metabolic requirements and the demands of molt, even when water was moderately warm. Efectos de la Muda Rápida de las Plumas de Vuelo Sobre la Dispersión Post-Reproductiva en un Ave Marina que se Zambulle para Perseguir Presas

Post-release survival of surf scoters following an oil spill: An experimental approach to evaluating rehabilitation success

Birds are often the most numerous vertebrates damaged and rehabilitated in marine oil spills; however, the efficacy of avian rehabilitation is frequently debated and rarely examined experimentally. We compared survival of three radio-marked treatment groups, oiled, rehabilitated (ORHB), un-oiled, rehabilitated (RHB), and un-oiled, non-rehabilitated (CON), in an experimental approach to examine post-release survival of surf scoters (Melanitta perspicillata) following the 2007 M/V Cosco Busan spill in San Francisco Bay. Live encounter-dead recovery modeling indicated that survival differed among treatment groups and over time since release. The survival estimate (±SE) for ORHB was 0.143±0.107 compared to CON (0.498±0.168) and RHB groups (0.772±0.229), suggesting scoters tolerated the rehabilitation process itself well, but oiling resulted in markedly lower survival. Future efforts to understand the physiological effects of oil type and severity on scoters are needed to improve post-release survival of this species.

At-sea Activity and Diving Behavior of a Radio-tagged Marbled Murrelet in Central California

Abstract Radio-telemetry was used to continuously monitor the at-sea activity of an adult Marbled Murrelet (Brachyramphus marmoratus) nesting in Santa Cruz County, California. From 05.39 h on 28 May 1997, to 05.14 h on 29 May 1997, the murrelet was followed by tracking teams at Año Nuevo Bay. Between 05.44 h and 20.19 h on 28 May, the bird engaged in eleven dive bouts, with a mean duration of 18.8 ± 5.4 min. Mean dive duration was 24.8 ± 15.7 s; mean surface between dives was 15.2 ± 12.7 s. No dives were initiated after 20.19 h. The bird spent 12.3% of the at-sea period and 23.4% of daylight hours engaged in diving bouts. This relatively small amount of time spent diving allows for considerable flexibility in activity budget.

THE HIGH COST OF MOTHERHOOD: END-LACTATION SYNDROME IN SOUTHERN SEA OTTERS (ENHYDRA LUTRIS NEREIS) ON THE CENTRAL CALIFORNIA COAST, USA.

Abstract Sea otters (Enhydra lutris) have exceptionally high energetic requirements, which nearly double during lactation and pup care. Thus, females are extremely vulnerable to caloric insufficiency. Despite a number of compensatory strategies, the metabolic challenge of reproduction culminates in numerous maternal deaths annually. Massive depletion of energy reserves results in a case presentation that we define as end-lactation syndrome (ELS), characterized by moderate to severe emaciation not attributable to a concurrent, independent disease process in females dying during late pup care or postweaning. We compiled detailed data for 108 adult female southern sea otters (Enhydra lutris nereis) examined postmortem that stranded in California, US, 2005–12, and assessed pathology, reproductive status, and the location and timing of stranding. We introduce simple, grossly apparent, standardized physical criteria to assess reproductive stage for female sea otters. We also describe ELS, examine associated risk factors, and highlight female life history strategies that likely optimize reproduction and survival. Our data suggest that females can reset both the timing and energetic demands of reproduction through fetal loss, pup abandonment, or early weaning as part of specific physiologic checkpoints during each reproductive cycle. Females appear to preload nutritionally during delayed implantation and gestation to increase fitness and reproductive success. We found that ELS was a major cause of death, affecting 56% of enrolled adult females. Peak ELS prevalence occurred in late spring, possibly reflecting the population trend toward fall/winter pupping. Increasing age and number of pregnancies were associated with a higher risk of ELS. Although the proportion of ELS females was highest in areas with dense sea otter populations, cases were recovered throughout the range, suggesting that death from ELS is associated with, but not solely caused by, population resource limitation.

Investigation of a Largescale Common Murre (Uria aalge) Mortality Event in California, USA, in 2015

Abstract:  From August through December 2015, beachcast bird survey programs reported increased deposition of Common Murres (Uria aalge) on central and northern California beaches, but not on southern California beaches. Coastal wildlife rehabilitation centers received more than 1,000 live, stranded, and debilitated murres from Sonoma County to San Luis Obispo County during August–October. Approximately two-thirds of admitted birds were after-hatch-year birds in emaciated body condition and in various stages of molt, with extremely worn plumage. Necropsies were done on a sample (n=35) of birds to determine the probable cause of death of beachcast carcasses. Most birds examined during necropsy were emaciated, with starvation the most likely cause of death. Birds were also tested for underlying infectious diseases at the US Geological Survey National Wildlife Health Center and harmful algal bloom toxins at the University of California at Santa Cruz and the National Oceanographic and Atmospheric Administrations Northwest Fisheries Science Center. Twenty-four out of 29 tested birds had detectable levels of domoic acid, and no indication of infectious disease was found. Emaciation is thought to be the cause of death for these birds, with a large warm water anomaly and harmful algal bloom playing a secondary detrimental role.

Revisiting Winter Wing Molt in Western Grebes (Aechmophorus occidentalis) and Clark's Grebes (A. clarkii)

Abstract. Species that undergo simultaneous flight-feather molt are susceptible to mortality during the flightless period. Remigial molt was examined in non-breeding Western Grebes (Aechmophorus occidentalis) and Clarks Grebes (A. clarkii) using beachcast carcasses from California to Washington to determine wrhere and when molt occurs and help identify regions of maximum risk. Molt occurred in 18% of individuals and in all age classes and months examined, including winter, not previously recognized as a significant period for Western and Clarks grebe molt. Molt was encountered in all regions, with the highest proportions in Oregon/Washington during fall (35%), and central (18%) and southern (17%) California during winter. The percentage of Western and Clarks grebes in molt collected during the first 3 days of an oil spill was greater than later in the response (27% vs. 12%), suggesting a greater vulnerability to oiling during this part of their life cycle. Oil spills and other mortality events can provide insights into avian biology not otherwise available, and knowledge of molting regions can minimize wildlife impacts of spills through prevention and response. Received 15 November 2012, accepted 6 August 2013.

Life and Death: How Should We Respond to Oiled Wildlife?

Abstract There is ongoing public debate about the best course of action to take when wildlife are affected by oil spills. Critics of wildlife rehabilitation suggest that the cleaning and release of...

POST-RELEASE MONITORING OF OILED BROWN PELICANS FROM THE 2015 REFUGIO OIL SPILL

ABSTRACT A great deal of effort and resources is expended on the cleaning and rehabilitation of oiled wildlife, but the ultimate fate of these animals is often unknown. Post-release monitoring is e...