Harry R. Carter

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.

ESTIMATING MORTALITY OF SEABIRDS FROM OIL SPILLS

ABSTRACT From an aesthetic and damage assessment standpoint, the loss of seabirds may be one of the more important results of a marine oil spill. Assessment of the actual numbers of seabirds killed is difficult because the bodies of dead or incapacitated seabirds are often never found or recorded. We present a computer methodology that estimates the number of birds that come in contact with an oil spill and partitions these birds among four possible fates: (1) swimming or flying ashore under their own power; (2) carried out to sea by winds and currents; (3) carried inshore, but lost before being beached; and (4) beached by winds and currents. Beached birds are further divided into those that are recovered and those that are not. The accuracy of the methodology is examined using data for two recent spills in central California, each of which resulted in the beachings of large numbers of birds. The methodology also has potential application to real-time emergency response by predicting when and where the gr...

FORAGING DISTANCE AND HOME RANGE OF CASSIN'S AUKLETS NESTING AT TWO COLONIES IN THE CALIFORNIA CHANNEL ISLANDS

Abstract We radio-marked 99 Cassins Auklets (Ptychoramphus aleuticus) nesting at two colonies, Prince Island and Scorpion Rock, separated by 90 km in the California Channel Islands to quantify foraging distance, individual home-range area, and colony-based foraging areas during three consecutive breeding seasons. Auklets generally foraged <30 km from each colony in all years. Core foraging areas (50% fixed kernel) from Prince Island in 1999–2001 were north to northeast of the colony over the insular shelf near the shelfbreak. Core foraging areas from Scorpion Rock in 2000–2001 occurred in two focal areas: the Anacapa Passage, a narrow interisland passage adjacent to the colony, and over the southeastern Santa Barbara Channel. During 2000, intercolony foraging areas overlapped by 10%; however, auklets from each colony used the overlapping area at different times. Equivalent-sample-size resampling indicated Prince Island foraging area (1216 ± 654 km2) was twice that of Scorpion Rock (598 ± 204 km2). At Prince Island, mean individual distances, home-range areas, and colony-based activity areas were greater for females than males, especially during 2001. At Prince Island, core foraging areas of females and males, pooled separately, overlapped by 63% in 1999 and 2000, and by 35% in 2001. Postbreeding auklets from both colonies dispersed northward and moved to active upwelling centers off central California, coincident with decreased upwelling and sea-surface warming throughout the Santa Barbara Channel. Distancias de Forrajeo y Rangos de Hogar de Dos Colonias de Nidificación de Ptychoramphus aleuticus en las Islas del Canal de California Resumen. Para cuantificar la distancia de forrajeo, el área de hogar de los individuos y las áreas de forrajeo de las colonias, marcamos con radiotransmisores 99 individuos de la especie Ptychoramphus aleuticus que estaban anidando en dos colonias separadas por 90 km en las islas del Canal de California (Prince Island y Scorpion Rock) durante tres temporadas reproductivas consecutivas. Las aves generalmente forrajearon a menos de 30 km de cada colonia en todos los años. Las áreas núcleo de forrajeo (“kernel” fijo del 50%) de la colonia de Prince Island en 1999–2001 se ubicaron al norte y al noreste de la colonia, cerca del borde de la plataforma insular. Las áreas núcleo de la colonia de Scorpion Rock en 2000–2001 se ubicaron en dos áreas focales: el Pasaje de Anacapa, un estrecho corredor marítimo entre islas adyacente a la colonia, y en el sureste del Canal de Santa Barbara. Durante 2000, las áreas de forrajeo de las dos colonias se superpusieron en un 10%, pero las aves de cada colonia utilizaron las áreas de superposición en momentos diferentes. Análisis con tamaños de muestra equivalentes indicaron que el área de forrajeo de Prince Island (1216 ± 654 km2) era el doble de Scorpion Rock (598 ± 204 km2). En Prince Island, las distancias promedio entre individuos, el tamaño de los rangos de hogar y las áreas en que la colonia centró sus actividades fueron mayores para las hembras que para los machos, especialmente durante 2001. En Prince Island, las áreas núcleo de forrajeo de hembras y machos, combinadas separadamente, se superpusieron en un 63% en 1999 y 2000, y en un 35% en 2001. Las aves post-reproductivas de ambas colonias se dispersaron hacia el norte y se desplazaron hacia centros activos de surgencia en aguas de California central, de forma coincidente con una disminución en la surgencia y un calentamiento de la superficie del mar a través del Canal de Santa Barbara.

Costs of adoption in Western Gulls

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Creching Behavior of Brandt's Cormorant Chicks

Creching behavior of Brandts Cormorant (Phalacrocorax penicillatus) chicks was studied at Southeast Farallon Island, California, in July and August 1984. Three stages of creching were described: (1) nest-site creches involved small chicks (10 to 25 days old) from adjacent nests huddling on nest sites before and just after parents stopped continuous attendance of chicks; (2) subcolony creches involved medium-sized chicks (over 20 days old) standing together between nest sites and on the periphery of natal subcolonies; and (3) fledgling creches involved large chicks (over 25 days old) from several subcolonies standing together outside of subcolonies and nearer to the ocean. Nest-site creches occurred mainly at night and probably have a thermoregulatory function. Fledgling creches occurred throughout the day and night and may facilitate fledging behaviors. Chicks in fledgling creches entered the ocean, swam, dove, bathed, and returned to these creches where they were fed by adults up to and beyond the time when they could fly.

Rangewide Population Genetic Structure of Xantus's Murrelet (Synthliboramphus hypoleucus)

ABSTRACT. Population genetic structure was characterized in Xantuss Murrelet (Synthliboramphus hypoleucus) by analyzing variation in the mitochondrial control region (505 samples) and 12 microsatellite loci (428 samples) in birds captured at all 13 current breeding areas in southern California and northwestern Baja California, Mexico. The two types of molecular markers were consistent in revealing strong genetic differentiation between the two currently recognized subspecies (S. h. hypoleucus and S. h. scrippsi) and little or no differentiation among breeding areas within subspecies. Estimates of gene flow were essentially zero, and no evidence for admixture was found. Gene flow among breeding locations within subspecies, on the other hand, was seemingly high. Given these genetic results, as well as clear morphological differences between the subspecies and the apparent lack of interbreeding at breeding areas where the two forms are sympatric, we suggest that two species be recognized. Both forms are genetically distinct from Craveris Murrelet (S. craveri), a closely related species whose breeding range partially overlaps that of Xantuss Murrelet. Taxonomic subdivision of Xantuss Murrelet introduces new conservation concerns, especially for S. h. hypoleucus, which urgently requires greater study and protective efforts.

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.

Nesting ecology of Marbled Murrelets at a remote mainland fjord in southeast Alaska

ABSTRACT Studying the ecology of endangered species in portions of their range where the population remains abundant can provide fundamental information for conservation planners. We studied nesting by radio-tagged Marbled Murrelets (Brachyramphus marmoratus) during 2007 and 2008 in Port Snettisham, a relatively pristine, remote mainland fjord in southeast Alaska with high at-sea densities of Marbled Murrelets during the breeding season. Of 33 active Marbled Murrelet nest sites located during the study, we found 15 within forested habitat (tree nest sites), 16 in nonforested habitat (ground nest sites), and 2 that could not be determined. Some nests were located farther inland from the coast (range: 1–52 km) and at higher elevations (range: 42–1,100 m) than previously documented in Alaska. Nesting success to ≥20 days posthatch (0.20 ± 0.07 [SE]) was less than half of similar estimates in British Columbia and more comparable to estimates from California and Washington. A logistic regression found that nesting success did not differ between years, but nesting success was higher for tree nests than for ground nests. Conservation planners should consider that Marbled Murrelets will use certain nonforest habitat types for nesting in mainland southeast Alaska. Our reported nesting success was likely a maximum, and our results indicate that nesting success can be low even when nesting habitat is seemingly abundant and marine habitat appears excellent.

Decline of the Marbled Murrelet in Clayoquot Sound, British Columbia: 1982-1993

In 1992 and 1993, we repeated at-sea surveys of marbled murrelets (Brachyramphus marmoratus) in Clayoquot Sound, British Columbia, that were conducted originally in 1982. Murrelet distribution was determined by counting birds in 341 contiguous l-km2 quadrats in fiord, channel, and inshore marine habitats. Counts for this area totaled 4500 birds in 1982, 2704 birds in 1992, and 2622 birds in 1993 which constituted a 40% decline in the population size from 1982-1993. Birds were clumped in all surveys, with the highest densities in inshore (28, 14.3, 7.85 birds/km2 in 1982, 1992, and 1993, respectively) and channel (11.8, 9.1, 14.2 birds/ km2 in 1982, 1992, and 1993, respectively) marine habitats. The average change in the number of birds in each quadrat between the 1982 and 1992-93 surveys was significant for all quadrats combined, and individually for inshore quadrats. We consider the loss of nesting habitat in oldgrowth forest to be the probable cause of most of the observed population decline. By 1992 approximately 15-24.5% of the originally forested area in Clayoquot Sound had been logged. Oil spills, gill-net fishing, and oceanographic conditions (E1 Nino) were also considered as possible factors contributing to the population decline. This study is the first in North America to document a decline in a marbled murrelet population using a single, standardized at-sea survey technique. Marbled murrelets (Brachyramphus marmoratus) nest on tree branches in the canopies of oldgrowth and mature forests from southern Alaska to California (see recent su maries in Singer et al. 1991, Carter and Morrison 1992, Ewins et al. 1993, Hamer and Nelson 1995a). Standardized methods have been developed to monitor the activity of birds at inland nesting locations (e.g., Paton et al. 1990), but nests are difficult to locate and population size must be determined and monitored using surveys at ocean foraging areas (Sealy and Carter 1984). Previous to 1982, few at-sea surveys had been conducted for this species, and population size and distribution still are incompletely known for most areas on the west coast of North America (Carter and Morrison 1992). Thus, it has been difficult to document population trends for this species related to the loss of old-growth forest nesting habitat and mortality from oil spills and gill-net fishing. These threats are cause for concern and have led to the recent federal listing of the marbled murrelet as threatened in British Columbia, Washington, Oregon and California (Rodway 1990, U.S. Fish and Wildlife Service 1992) and state listing as endangered in California (California Fish and Game Commission 1992). In British Columbia, portions of the coast have been surveyed for marbled murrelet populations (Carter 1984, Sealy and Carter 1984, Kaiser et al. 1991, Lawrence and Backhouse 1991, Savard and Lemon 1992). Provincial estimates of 45,000-50,000 breeding birds (Rodway et al. 1992) are poorly substantiated for the most part because many areas have not been surveyed and survey data have been difficult to convert into reliable population estimates (Rodway et al. 1992, 1995). In addition, marbled murrelet populations have been considered to have declined in some areas in the province, based on anecdotal evidence (Brooks 1926, Pearse 1946) and loss of nesting habitat, yet quantitative data have not been available to investigate the degree of possible declines. Estimates of population size for large geographic areas have been published only for Clayoquot and Barkley sounds on the west