Richard T. Golightly

Assessment of Social Attraction Techniques Used to Restore a Common Murre Colony in Central California

Abstract Colonial seabirds such as alcids often do not rapidly recolonize former breeding habitat following extirpation of nesting colonies. Social attraction (e.g., use of decoys, recorded vocalizations and mirrors) artificially stimulates nesting by providing social cues that encourage colonization. Common Murres (Uria aalge) stopped breeding at Devil’s Slide Rock, San Mateo County, California following the 1986 Apex Houston oil spill. Natural recolonization did not occur between 1987 and 1995. Common Murres began regular visits to Devil’s Slide Rock within 24 hours of social attraction equipment installation in January 1996 and six pairs nested by June 1996. Over 90% of murre observations were in decoy plots in contrast to control plots and outside of plots where few murre observations occurred. Significantly more murre presences versus absences were recorded in low density decoy plots and these birds most often frequented open areas (aisles) within decoy clusters. Significantly larger groups of murres visited high density decoy plots and aisle sub-plots. Murre densities were significantly greater within 30 cm of mirrors. Five of six nests were within 60 cm of mirrors. Nests coincided with areas where prior nesting and last pre-1996 attendance had been concentrated. Rapid breeding response combined with recent nonbreeding attendance suggests that the first colonists may have been surviving breeders from the original colony or young produced at the rock prior to the oil spill. The initial recolonization event and continued restoration efforts have prompted further colony growth to 190 pairs nesting by 2004. This study suggests that social stimuli can limit natural colonization of otherwise suitable habitat.

Effects of radiotransmitters on the reproductive performance of Cassin’s auklets

Abstract We examined whether radiotransmitters adversely affected the reproductive performance of Cassin’s auklets (Ptychoramphus aleuticus) breeding on the California Channel Islands during 1999-2001. We attached external radiotransmitters to 1 partner in 108 Cassin’s auklet pairs after nest initiation and used 131 unmarked, but handled, pairs as controls. Compared to alpha chicks raised by radiomarked pairs, alpha chicks raised by unmarked pairs had faster mass growth rates (1.95 ± 0.30 g d-1 vs. 3.37 ± 0.53 g d-1, respectively), faster wing growth rates (2.46 ± 0.10 mm d-1 vs. 2.85 ± 0.05 mm d-1), greater peak fledging masses (118.9 ± 3.5 g vs. 148.3 ± 2.4 g), and higher fledging success (61% vs. 90%). Fledging success was reduced more when we radiomarked the male (50% fledged) rather than the female partner (77% fledged). After fledging an alpha chick, unmarked pairs were more likely to initiate a second clutch (radiomarked: 7%; unmarked: 39%) but did not hatch a second egg (radiomarked: 4%; unmarked: 25%) or fledge a second (beta) chick (radiomarked: 4%; unmarked: 18%) significantly more often than radiomarked pairs. We resighted 12 radiomarked individuals nesting during a subsequent breeding season; each bird had shed its transmitter and healed the site of attachment. We suggest caution in using telemetry to evaluate the reproductive performance of alcids, but marking only females may minimize adverse effects.

Characterizing dispersal patterns in a threatened seabird with limited genetic structure.

Genetic assignment methods provide an appealing approach for characterizing dispersal patterns on ecological time scales, but require sufficient genetic differentiation to accurately identify migrants and a large enough sample size of migrants to, for example, compare dispersal between sexes or age classes. We demonstrate that assignment methods can be rigorously used to characterize dispersal patterns in a marbled murrelet (Brachyramphus marmoratus) population from central California that numbers approximately 600 individuals and is only moderately differentiated (FST∼ 0.03) from larger populations to the north. We used coalescent simulations to select a significance level that resulted in a low and approximately equal expected number of type I and II errors and then used this significance level to identify a population of origin for 589 individuals genotyped at 13 microsatellite loci. The proportion of migrants in central California was greatest during winter when 83% of individuals were classified as migrants compared to lower proportions during the breeding (6%) and post‐breeding (8%) seasons. Dispersal was also biased toward young and female individuals, as is typical in birds. Migrants were rarely members of parent‐offspring pairs, suggesting that they contributed few young to the central California population. A greater number of migrants than expected under equilibrium conditions, a lack of individuals with mixed ancestry, and a small number of potential source populations (two), likely allowed us to use assignment methods to rigorously characterize dispersal patterns for a population that was larger and less differentiated than typically thought required for the identification of migrants.

Radio-Telemetry Evidence of Re-nesting in the Same Season by the Marbled Murrelet

Abstract Unlike other alcids, laying of replacement eggs has not been well documented in Brachyramphus murrelets. Observations of two radio-marked Marbled Murrelets (Brachyramphus marmoratus) in northern California during 2001 and 2002 suggested that they can re-lay in the same breeding season. In 2001, aircraft telemetry first detected a male Marbled Murrelet at a forested inland location on 17 May. This bird alternated 24h incubation bouts with 24h at sea periods until 29 May, when data logger recordings indicated that the bird arrived at the nest at 05.17 h (PDT), but left at 05.32 h. This nesting effort had apparently failed. Sixteen days later, on 14 June this murrelet arrived in the vicinity of the first nest site at 05.19 h and remained there until 18.57 h that same evening and then left. We suspected that this event represented a second breeding effort that also failed, either near or at the site of the first effort. In 2002 a female Marbled Murrelet, first detected inland on 13 June by aircraft telemetry, alternated on the nest one day and at sea the next until 23 June when the breeding effort is presumed to have failed. This bird was again detected inland on 21 July, and alternated on the nest one day and at sea the following day until 3 August, when the radio-transmitter fell off the bird. Video recordings at the nest site indicated this second nesting attempt continued until 1 September, when the chick died of unknown causes. As in other alcids, re-laying apparently occurred 2-4 weeks after failure of the first eggs, either near or at the site of first eggs. Re-nesting may be frequent in murrelets, given the high rates of breeding failure reported.

Energy and nutrient assimilation by gray foxes on diets of mice and Himalaya berries

Digestible and assimilated energy and other nutrients derived from mice ( Mus musculus ) and Himalaya berries ( Rubus procerus ) were compared in the diet of five gray foxes ( Urocyon cinereoargenteus ) held in outdoor enclosures. Percent digestible and metabolizable energy of mice on a dry-weight, ash-free basis (93.0 ± 0.8%, 86.0 ± 1.4%, respectively; X ± SE ) were significantly greater than that of berries (49.7 ± 7.3%, 22.0 ± 10.8%). Digestible crude fat and crude protein were significantly greater ( P < 0.001) for diets composed of mice than of berries. Foxes were in a negative energy and protein balance when they consumed the berry diet. Although gray foxes in northern California consume berries during summer, they would have difficulty meeting energy and nutrient requirements on an exclusively frugivorous diet.

Mark–resight density estimation for American black bears in Hoopa, California

Abstract Accurate and precise population estimates are necessary to answer many management questions, but these estimates are generally unavailable for large carnivores because of their extensive movements, low densities, and secretive natures. These traits also often prevent the bounding of occupied areas necessary to estimate densities. We used a modified Petersen mark–recapture methodology to estimate black bear density in 1998 at 2 study sites on the Hoopa Valley Reservation, California, from mark–resight data. We used culvert traps to capture, radiocollar, and eartag bears, radio telemetry to establish closure, and remote cameras to collect resighting data. We calculated bear densities (90% confidence intervals) of 0.18 (0.09–0.32) and 1.33 (0.54–3.29) bears/km2 on the 2 sites. Knowledge of bear densities can now be incorporated into forest management actions and associated bear control measures on the Hoopa Valley Reservation.

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.

DIET OF XANTUS'S MURRELETS IN THE SOUTHERN CALIFORNIA BIGHT

Abstract Most of what is known about diet of Xantuss Murrelets (Synthliboramphus hypoleucus) comes from prey found in 19 of 22 murrelet stomachs collected during the 1977 breeding season near Santa Barbara Island in the Southern California Bight (SCB). In May 2002, we examined stomachs of 10 Xantuss Murrelets collected near Anacapa Island, also within the SCB. Seven of the 10 stomachs contained prey. Prey were subadult or adult northern anchovy (Engraulis mordax; 2 stomachs), either juvenile bluefin driftfish (Psenes pellucidus) or medusafish (Icichthys lockingtoni; 2 stomachs), and euphausiids (Thysanoessa spinifera; 3 stomachs). Only one prey type was found in each stomach. Our sample added to the diversity of known prey types used in the SCB, including euphausiids and larger age/size classes of fish. We confirmed continued use of northern anchovy, and identified new prey species (bluefin driftfish or medusafish) associated with jellyfish or floating algae and debris in convergence lines. During the breeding season, Xantuss Murrelets appear to be generalist feeders that search for and use available prey that may be concentrated at convergence lines.

Behavioral and Ecological Adaptations to Water Economy in Two Plethodontid Salamanders, Ensatina eschscholtzii and Batrachoseps attenuatus

Abstract Amphibians in general, and plethodontid salamanders in particular, are highly susceptible to cutaneous water loss. We compared behavior, habitat use, and physiology of Batrachoseps attenuatus (Eschscholtz) and Ensatina eschscholtzii (Gray) in Humboldt County, California, to identify adaptations of water economy. Both species lost more body water in a dry environment than in a wet one. In the field, sites with salamanders had higher relative humidity than sites without salamanders. In behavioral experiments, both species used water-conserving postures; they positioned themselves deep in leaf litter in dry environments while remaining on the surface of leaf litter in wet environments. The slender morphology of B. attenuatus may aid in habitat partitioning by plethodontid salamanders; in the field we found B. attenuatus closer to the surface of the leaf litter than E. eschscholtzii. The evolution of a slender body shape appears to be unconstrained by microclimates typically encountered by this species.

Breeding Phenology and Reproductive Success of the Brandt's Cormorant at Three Nearshore Colonies in Central California, 1997-2001

Abstract Brandts Cormorant (Phalacrocorax penicillatus) breeding effort, phenology and success were studied in 1997-2001 at three colonies spanning approximately 200 km of the central California coast: Point Reyes (PR); Devils Slide Rock and Mainland (DS); and Castle-Hurricane Colony Complex (CH). Breeding effort was reduced at all three colonies in the 1998 El Niño event. Mean clutch initiation dates differed significantly among colonies, with cormorants at the southernmost colony (CH) laying earliest, and those at the northernmost colony (PR) laying latest. Productivity at individual colonies varied greatly among years (range 0.7-2.5 fledglings per pair). Overall colony means were lowest (1.6 fledglings/pair) during the 1998 El Niño event and highest (2.5 fledglings/pair) in the 1999 La Niña event. Productivity at CH (1.7 fledglings/pair) was significantly lower than at PR (2.2 fledglings/pair), and interannual variation was greatest at CH. Late-nesting birds laid fewer eggs, hatched fewer chicks, and fledged fewer chicks per pair than early-nesters. The rapid rate of growth at some nearshore colonies in central California suggests immigration from elsewhere, most likely the large offshore colony at the South Farallon Islands. Variation in timing of breeding and reproductive success among colonies demonstrates a value in maintaining multiple study locations when assessing Brandts Cormorant population parameters in the California Current System.