R. I. Guy Morrison

DECLINES IN WINTERING POPULATIONS OF RED KNOTS IN SOUTHERN SOUTH AMERICA

Abstract Surveys of the North American race of the Red Knot (Calidris canutus rufa) on its main wintering areas on the coasts of Patagonia and Tierra del Fuego (Argentina and Chile) showed a dramatic decline in the wintering population: totals in 2003 were about 30 000 compared to 67 500 in the mid-1980s. Numbers at the principal wintering site, Bahia Lomas, fell by approximately 50%, from 45 300 in 2000 to 22 000–25 000 in 2002–2003. Numbers at peripheral sites on the coast of Patagonia declined dramatically, decreasing 98% compared to numbers in the mid-1980s. The results showed that declines at core sites did not result from birds moving to other places within the known wintering (or other) areas, but reflected a general population decline, with most birds now restricted to key sites in Tierra del Fuego. This phenomenon may explain why long-term declines noted elsewhere have only recently become apparent at key wintering areas. Possible reasons for the declines are discussed. Banding studies in Delaware Bay have shown that in recent years an increasing proportion of Red Knots is unable to gain sufficient weight for migration to the breeding grounds. This is likely due to reductions in their main food resource, eggs of the horseshoe crab Limulus polyphemus. The resulting increase in mortality could account for the magnitude and severity of the declines we observed. Disminuciones en las Poblaciones Invernantes de Calidris canutus rufa en el Sur de Sur América Resumen. Censos de la raza norteamericana de Calidris canutus (rufa) en sus áreas de invernada principales en las costas de la Patagonia y Tierra del Fuego (Argentina y Chile) mostraron una disminución dramática en la población invernante. Los totales en 2003 fueron aproximadamente 30 000, comparados con 67 500 a mediados de los años 80. Los números en el sitio principal de invernada (Bahía Lomas) decayeron en aproximadamente un 50%, de 45 300 en 2000 a 22 000–25 000 en 2002–2003. Los números en sitios periféricos en la costa de Patagonia declinaron dramáticamente, en un 98% en comparación con los números de mediados de los ochenta. Los resultados mostraron que las disminuciones en los sitios núcleo no fueron el resultado de que las aves se movieran a otros sitios dentro del rango invernal conocido, o a otras áreas. En cambio, reflejaron una disminución general de la población; la mayoría de las aves están ahora restringidas a sitios claves en Tierra del Fuego. Este fenómeno podría explicar por qué las disminuciones poblacionales de largo plazo detectadas en otros lugares sólo se han hecho aparentes ahora en las áreas claves de invernada. Se discuten las posibles causas de las disminuciones. Estudios de anillamiento en la bahía de Delaware han mostrado que en años recientes una mayor proporción de las aves es incapaz de incrementar su peso hasta los niveles necesarios para la migración hacia las áreas de invernada. Esto probablemente es debido a reducciones en su principal recurso alimenticio, los huevos de Limulus polyphemus. El incremento en mortalidad resultante podría explicar la magnitud y la severidad de las disminuciones poblacionales que observamos.

Energy Expenditure and Water Turnover of Incubating Ruddy Turnstones : High Costs under High Arctic Climatic Conditions

To investigate whether shorebirds breeding in the High Arctic have relatively high rates of energy expenditure due to the harsh climatic conditions that prevail even in summer, we measured daily energy expenditure (DEE) and water turnover of Ruddy Turnstones (Arenaria interpres) during the incubation phase on Rowley Island in Foxe Basin, N.W.T., Canada, at 69-degrees-N, using the doubly-labeled-water technique. Simultaneously, we conducted detailed measurements of ambient climatic conditions, including in situ measurements with heated taxidermic mounts. A series of 11 doubly-labeled-water measurements with eight individual Ruddy Turnstones, of which at least seven successfully hatched eggs, yielded a mean DEE of 4.08 W. This is a relatively high value for a 108-g bird, equalling four times their basal metabolic rate (BMR). Most variation in DEE was attributable to standard operative temperature, which combines the effects of air temperature, wind and radiation on heat loss from the turnstones point of view. On average, 25% of DEE was attributable to BMR, 31% to the cost of thermoregulation, and 44% to the cost of activity. The average value for water turnover of 96.6 g/day is high compared to published values for other birds and confirms the large requirement for food (which is water-rich) of incubating Ruddy Turnstones. An analysis of the climatic conditions prevalent in Foxe Basin during the breeding seasons of Ruddy Turnstones, based on the 33-year period 1958-1990, indicated that they faced thermostatic hardships, defined as energy expenditure exceeding the maximum sustained working level (estimated at 4.5 times BMR), on 15% of the days. Climatic conditions were most severe in the early 1960s, but have improved since.

Baseline and Stress‐Induced Levels of Corticosterone during Different Life Cycle Substages in a Shorebird on the High Arctic Breeding Grounds

After a migratory flight of several thousand kilometers to their high arctic breeding grounds, red knots (Calidris canutus islandica, Scolopacidae) showed high baseline concentrations of plasma corticosterone (58 ng/mL). Such high baseline corticosterone levels may be conditional for the right behavioral and metabolic adjustments to environmental and social stresses that shorebirds experience on arrival in an unpredictable tundra breeding environment. Despite the high baseline levels of corticosterone, red knots still showed a marked stress response during the postarrival period, with corticosterone concentrations increasing significantly during a 60‐min period of confinement. Baseline levels of corticosterone declined as the breeding season progressed. Red knots with brood patches, that is, birds that had completed egg laying and commenced incubation, had a reduced adrenocortical response to the stress of confinement compared with red knots with no, or with half‐developed, brood patches. This is consistent with the idea that birds breeding in extreme environments with short breeding seasons may exhibit a decreased adrenocortical response to stressful events to prevent high corticosterone concentrations from inducing interruptions of reproductive behavior.

TRANSFORMATIONS AT HIGH LATITUDES: WHY DO RED KNOTS BRING BODY STORES TO THE BREEDING GROUNDS?

Abstract We examined changes in body composition of Red Knots (Calidris canutus islandica) following arrival on their High Arctic breeding grounds at Alert, Ellesmere Island, Canada. Knots arrived in late May and early June with large fat and muscle stores. In the next two weeks, fat and protein stores (pectoral muscles) declined, while increases occurred in gizzard, proventriculus, gut length, heart, liver, and possibly gonads. Most stores were used before egg laying occurred and were therefore not available for egg formation. Early development of ova in some females suggests that body stores may be incorporated into the earliest eggs. While stores may be used for survival when conditions are difficult after arrival, their rapid loss and the concomitant increase in other organs suggests that a major function may be to facilitate a transformation from a physiological state suitable for migration to one suitable, and possibly required, for successful breeding. Transformaciones a Altas Latitudes: ¿Por qué Calidris canutus islandica Lleva Reservas Corporales a los Sitios de Nidificación? Resumen. Examinamos los cambios en la condición corporal de individuos de Calidris canutus islandica luego de que éstos llegaran a sus territorios reproductivos a altas latitudes en el Ártico en Alert, isla Ellesmere, Canadá. Los individuos de C. c. islandica llegaron a fines de mayo y comienzos de junio con grandes reservas de grasa y músculo. Durante las dos semanas siguientes, las reservas de grasa y proteína (músculos pectorales) disminuyeron, mientras que la molleja, los proventrículos, el largo del intestino, el hígado y posiblemente las gónadas aumentaron de tamaño. La mayoría de las reservas fueron usadas antes del período de puesta de huevos, por lo que éstas no estuvieron disponibles para la formación de los huevos. En algunas hembras, el desarrollo temprano de los óvulos sugiere que las reservas corporales pueden ser incorporadas en los primeros huevos. Si bien las reservas pueden ser usadas para sobrevivir en el momento de la llegada cuando las condiciones son difí ciles, su rápida pérdida y el aumento concomitante en otros órganos sugiere que una de las funciones principales de las reservas podría ser facilitar la transformación de un estado fisiológico apropiado para la migración a un estado apropiado y posiblemente requerido para la reproducción exitosa.

Dramatic Declines of Semipalmated Sandpipers on their Major Wintering Areas in the Guianas, Northern South America

Abstract. In the 1980s, aerial surveys in South America established that the main wintering areas of Semipalmated Sandpipers (Calidris pusilla) were found on the north coast of the continent, especially in the Guianas (Suriname, French Guiana and Guyana). Although population trend analyses have consistently shown declines in numbers of Semipalmated Sandpipers, especially for birds on migration in eastern North America, until now surveys had not been undertaken to determine whether such declines were reflected in numbers on the main wintering areas. Between December 2008 and January 2011, aerial surveys of major wintering areas in Suriname (3), French Guiana (2) and Guyana (1) were carried out. Results showed dramatic declines, with an overall total of only 21% of the 1980s total—a decrease of 79%. A variety of reasons may have contributed to the declines and include habitat changes, range shifts, sustained hunting, or increases in predation, pollution or severe weather.

Global-scale shorebird distribution in relation to productivity of near-shore ocean waters

-The median density of shorebirds during their non-breeding season on the coast of South America was significantly greater in coastal zones with high primary productivity than in zones with moderate and low primary productivity. A world-wide review showed that sites harboring large numbers of wintering and migratory shorebirds corresponded significantly with regions of high coastal zone productivity. We suggest that the spacing of rich intertidal foraging habitats along the worlds coastlines has been an important feature in the evolution of long distance migration by shorebirds. Received 16 November 2000, accepted 20 December 2000.

Population Trends in Semipalmated Sandpipers from Migration Counts

Abstract. Although Semipalmated Sandpipers are one of the most common shorebirds in North America, analyses of migration trends using data from the Maritimes, International and Ontario Shorebird Surveys, as well as the Quebec Checklist, collected between 1974–1998, consistently showed negative trends. An additional eleven years of data was assessed to determine if declines were ongoing. Analysis (Pearson correlation) of the Quebec Checklist data indicated a significant decline overall, from 1976 to 2008, and the percentage of checklists reporting flocks of >1,000 birds has decreased significantly since the 1970s. New analyses of population trends with migration monitoring data from eastern and central North America were conducted for the 35-year period from 1974 to 2009, using program ESTEQNINDEXE. Trends, although generally negative, were not statistically significant. In the North Atlantic region, where survey sites had the highest counts of Semipalmated Sandpipers, average abundance indices showed a pronounced decrease between 1985 and 1999 and an increase since then. Although the trend was not statistically significant, declines in Ontario amounted to an estimated 8% per year from 1974 to 2009. Counts were variable for Semipalmated Sandpipers in the Midcontinent region, although average abundance indices appeared lower in the second half of the analysis period (1989–2009). Thus, the population status of Semipalmated Sandpipers in North America may have improved since the 1990s, at least in the east.

Population Trends of Shorebirds in Southern Ontario, 1974–2009

Abstract. Shorebirds are thought to be declining across North America but trend analyses for migrant shorebirds at interior sites in eastern North America have not been updated since the late 1990s. Data from a volunteer-based survey at stopover sites throughout Ontario were used to assess population trends of shorebirds over the period 1974–2009. Surveyors carried out 7,135 surveys of 258 sites and recorded 538,744 individuals of 43 shorebird species. Of 19 taxa for which trends were estimated, 17 appeared to be declining in abundance. Precision of the trend estimates was generally poor and only three declines were significant at &agr; = 0.05. Total numbers of shorebirds recorded on surveys declined by four per cent per year, resulting in an estimated decrease in abundance of greater than 75% over the 35 years of observation. Rate of decline may be increasing for some species as declines for twelve species were larger for the period 1989–2009 vs. 1974–1989, and six species showed significant declines in the latter period whereas none did in the former period. Relating these declines in abundance at the surveyed sites to population declines is complicated by several potential sources of survey bias including changes in turnover rates and in migration timing and distributions of the species. However, given that these results are consistent with those of other migration surveys as well as those on the breeding and the wintering grounds, the most parsimonious explanation remains a widespread decline in shorebird populations.

Estimating Eastern Pacific Coast Populations of Whimbrels and Hudsonian Godwits, with an Emphasis on Chiloé Island, Chile

Abstract. A large proportion of the Hudsonian Godwits (Limosa haemastica) spending the boreal winter along the eastern Pacific Ocean coast are known to occur in the vicinity of Chiloé Island, Chile, but the importance of the region to Whimbrels (Numenius phaeopus) is less known. Ground counts conducted in 2007 and 2008 increased published estimates, at a minimum, of Pacific coast populations by 27% for Whimbrels (33,150 individuals) and 51% for Hudsonian Godwits (21,161 individuals). Bays and shorelines in the Chiloé Island region supported 99% of Hudsonian Godwits and, perhaps, 61% of Whimbrels estimated to occur along the Pacific coast during the boreal winter. Whereas Hudsonian Godwits aggregated in shallow bays on the eastern and northern coast of Chiloé Island, Whimbrels were more dispersed along the islands coastline and reached a density of 7.5 birds/km along sheltered gravel shorelines. Bays in the vicinity of Chiloés capital, Castro, provided important foraging and roosting habitat for non-breeding birds; these sites supported 52% of the Pacific coast population of Hudsonian Godwits and >4,000 Whimbrels. Low human disturbance in Pullao and Putemún bays makes these sites particularly attractive to nonbreeding Hudsonian Godwits, and their permanent protection is urged.

Reverse Movements of Red Knots Calidris canutus During Northward Migration in Argentina

SUMMARY. Migratory birds are sometimes known to make reverse movements to seek better fuelling sites before undertaking long-distance migratory flights across ecological barriers. Red knots Calidris canutus rufa regularly make prodigious migratory flights of ∼ 8,000 km from southern South America to North America; these flights depend critically on the birds being able to store adequate fuel at southern staging sites. Knots staging at San Antonio Oeste (SAO) in northern Patagonia in Argentina could potentially backtrack ∼200 km southwards to complete refuelling at Península Valdés (PV). We therefore analysed resightings of birds individually marked in SAO or the flyway at these two staging sites in 2006, 2007, 2009 and 2010 to investigate whether reverse movements occurred between them. In the four-year period, 63 detected individuals backtracked south from SAO to PV in one or more years. These movements occurred in all years of the study thus demonstrating the annual occurrence of flights of ∼200 km in the opposite direction to the normal northward migration. There was no significant difference in body condition (mass), sex or day of first sighting in SAO between birds that made or did not make reverse movements to PV. However, individuals (N = 11) that backtracked to PV from SAO had significantly lower hematocrit levels at the time of capture than SAO resident birds (N = 205). Because migrating shorebirds have been shown to restore low hematocrit levels before undertaking rapid fuel storage to power long flights, we hypothesise that red knots backtracking to PV were probably behind schedule on migration, and thus may have traded-off the small cost of a ∼200 km flight for the increased foraging time and high quality soft-shell prey available late in the season at PV. This hypothesis helps to explain the later staging phenology of red knots using PV, and its role as an alternative staging area in the northward migration.