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Captive and field- tested techniques for radio-attachment in bald eagles.
Abstract
The effects of two radio transmitter attachment techniques on captive and one attachment technique on wild Bald Eagles (Haliaeetus leucocephalus) were studied. A Y-attachment method with a 160-g dummy transmitter was less apt to cause tissue damage on captive birds than an X-attachment method, and loosely fit transmitters caused less damage than tightly fit transmitters. Annual survival of wild birds fitted with 65-g transmitters via an X attachment was estimated at 90-95%. As a result of high survival, only five wild birds marked as nestlings were recovered. Two of these birds had superficial pressure sores from tight-fitting harnesses. It is recommended that a 1.3-cm space be left between the transmitter and the bird's back when radio-tagging post-fledging Bald Eagles. Additional space, perhaps up to 2.5 cm, is required for nestlings to allow for added growth and development.
... Conservative and accurate estimates are needed in my case, because the Hawaiian hawk is endangered and currently proposed for delisting. (Buehler et al. 1995, Vekasy et al. 1996 were also applied to at least one member of the pair (n = 14). I made a minimum of 20 separate visits and spent a minimum of 250 observer hours at each site to trap and identify birds. ...
... Birds were weighed, measured, and banded with a unique combination of color bands and a USFWS band. A backpack radio transmitter was attached using a break-away harness design modified from Buehler et al. (1995) and Vekasy et al. (1996). I added a medium-weight cotton thread "weak link" to the harness on the ventral surface of the bird that connected all four straps. ...
To provide the U.S. Fish and Wildlife Service (USFWS) with updated information
on the Hawaiian hawk (‘io, Buteo solitarius) for reconsideration of its current status
(endangered), I tested survey methodology, determined population size, distribution,
habitat availability, survival, fecundity, and finite rate of increase (λ) of ‘io during
1998 and 1999 on the island of Hawai‘i. I estimated the total population at 1,457 (SE
= 176.3) hawks. Birds were distributed broadly around the island, but highest
densities were found in mature native forest with a grass understory (0.0057 ‘io/ha). I
calculated that 58.7% of the island (614,405 ha) is useable habitat for ‘io. Of the
useable habitat, 31.8% (195,350 ha) is currently protected by State and Federal
forests, parks, and refuges. Based on an average density of 0.0024 ± 0.0008 ‘io/ha in
those areas, I calculated that protected areas currently support 469 ‘io (95% CI = 244-
901). I determined that the maximum number of ‘io found on the island prior to
human occupation was 1,313 (95% CI = 857-2,013). In all habitats combined, first
year and adult survival was 0.50 (SE = 0.0981) and 0.94 (SE = 0.0404), respectively.
In all habitats combined, fecundity was 0.23 (SE = 0.04) female young/breeding
female. Overall finite rate of increase (λ) was 1.0324 (SE = 0.0428). Elasticity
analyses showed adult survival as the most important parameter regulating finite
growth of this population. Based on current ‘io populations that are equal or larger in
size to populations prior to human contact, high adult survival, the protection of
substantial areas of habitat, a mean finite rate of increase ~ 1, resistance to avian
diseases found on the island, no evidence of negative impacts of contaminants, and
the birds ability to use human-altered landscapes and exotic prey, the population
appears viable. However, because of the short duration of this study, the relatively
low population size, the variance around my estimates, and environmental
stochasticity, I feel delisting is not warranted. I feel downlisting would be
appropriate for this species. Regardless of a change in listing, population size and
especially adult survivorship should be routinely monitored.
... Adult goshawks were captured at their nests using Dho-gaza nets and a live Great Horned Owl (Bubo virginianus) as lure ( Bloom et al. 1992). All hawks were fitted with an 18 g backpack style transmitter-harness package ( Buehler et al. 1995; 2-3% of body weight, Advanced Telemetry Systems, Isanti, MN). Transmitter batteries lasted up to four years and no premature failures were confirmed out of the 35 birds radiotagged during the study. ...
... Adult goshawks were captured at their nests using Dho-gaza nets and a live Great Horned Owl (Bubo virginianus) as lure ( Bloom et al. 1992). All hawks were fitted with an 18-g backpack style transmitterharness package (Buehler et al. 1995; 2-3% of body weight, Advanced Telemetry Systems, Isanti, MN). Transmitter batteries lasted up to three years and no premature failures were confirmed out of 35 birds radiotagged during the study. ...
... Ravens used in this study were trapped at 16 different locations (11 of which were inside Yellowstone National Park), and it often took hours or even several days before ravens landed in front of the trap. We fitted solar-powered GPS transmitters (e-obs GmbH; Bird Solar UMTS, 25 g) on ravens as backpacks with a Teflon harness (after Buehler et al., 1995) that weighed 35-37 g (i.e., 3.1%-3.7% of the raven's body mass). The GPS transmitters recorded data between approximately sunrise and sunset at 30-minute intervals with fully charged batteries (i.e., above 3,900 mV), at 1-hour intervals with a lower battery voltage (i.e., below 3,900 mV), and temporarily stopped GPS data collection when the voltage was extremely low (i.e., below 3,700 mV). ...
Anthropogenic food subsidies can alter ecosystem processes, such as competition, predation, or nutrient transfer, and may strongly affect protected areas. Increasing recreation and ecotourism often create food subsidies, especially in the surrounding lands through fast-growing gateway communities. How the effects of these subsidies extend into protected areas when animals move across boundaries remains largely unexplored. We addressed this question by studying the movement and foraging of common ravens ( Corvus corax) , opportunistic scavengers that are well known to feed on predator kills and on anthropogenic food subsidies. We analyzed spatiotemporal data from 57 global positioning system (GPS)-tagged ravens, trapped within or close to Yellowstone National Park, to study their seasonal use of natural and anthropogenic food sources. Although Yellowstone National Park contains a full suite of native predators and ravens can be observed at virtually every kill site, we show that anthropogenic subsidies were utilized to a much greater extent than other natural resources, especially during winter. Important subsidies included gut piles of harvested game animals left by hunters, fat present on wastewater settling ponds, roadkill, and waste from agricultural and urban activities. These subsidies were distributed over vast areas beyond Yellowstone National Park. During fall/winter, ravens traveled longer distances (21.9 vs. 13 km) and spent more time outside Yellowstone National Park (73% of GPS points outside), mostly feeding on anthropogenic subsidies, than in spring/summer (42% of GPS points outside). This difference between seasons was more pronounced for individuals holding territories within the protected area than for those without territories. The large area over which ravens used anthropogenic food subsidies (within more than 100 km of Yellowstone National Park) affects the park’s raven population and the scavenging services they provide. We suggest that the scale of resource use must be considered by managers seeking to control expanding raven populations elsewhere.
... At both locations, upon capture, we weighed and banded each individual with a USGS band and either an alpha-coded (Ohio) or color (Washington, D.C.) band, and attached a satellite transmitter. We attached one of three types of transmitters, including a battery-powered satellite transmitter, solarpowered satellite transmitter, or solar-powered GPS-GSM transmitter (Global System for Mobile Communications; Table 1), with a backpack harness made of Teflon ribbon (Buehler et al. 1995). All transmitters with harnesses weighed < 5% of bird mass. ...
en An understanding of the full annual cycle distributions of bird populations is a prerequisite to elucidating the drivers of differing trends among breeding populations. In the United States, Black-crowned Night-Herons (Nycticorax nycticorax) are listed as threatened or endangered in some states where they breed, but populations are stable in others. Outside of the breeding season, little is known about the species, including migratory routes and wintering areas. We used transmitters to track 28 Black-crowned Night-Herons from breeding colonies with stable (Washington, D.C.) and declining (Ohio) populations. For breeding populations across North America, we used band encounter data to estimate the movement of populations between breeding and wintering latitudes and the strength of migratory connectivity metric among latitudes. The first full annual cycle tracking of Black-crowned Night-Herons revealed diverse wintering strategies, including broad geographic distributions, within-winter movements, and between-year site fidelity. We found that over 80% of tracked individuals from the two breeding populations shared similar wintering areas, including the southern United States, Cuba, Honduras, and Nicaragua. Black-crowned Night-Herons exhibited weak breeding to wintering migratory connectivity (MC = 0.001 ± 0.03) across the latitudinal extent of their North American breeding range, including some degree of partial migration. High overlap in the winter distributions and within-winter relocations of Black-crowned Night-Herons tracked from breeding populations in the two regions, as well as weak migratory connectivity across their range, suggest that localized conditions during the winter period may not be driving different trends in breeding populations.
RESUMEN
es El seguimiento del ciclo anual completo de las garza nocturna de corona negra (Nycticorax nycticorax) sugiere que las áreas de invernada no explican las diferencias en las tendencias poblacionales de las colonias
La comprensión de las distribuciones del ciclo anual completo de las poblaciones de aves es un prerrequisito para dilucidar los promotores de las diferentes tendencias entre las poblaciones durante la reproducción. En los Estados Unidos, las garzas nocturnas de corona negra (Nycticorax nycticorax) están clasificadas como amenazadas o en peligro de extinción en algunos estados donde se reproducen, pero las poblaciones son estables en otros. Fuera de la temporada de reproducción, se sabe poco sobre esta especie, incluidas las rutas migratorias y las áreas de invernada. Usamos transmisores para rastrear 28 individuos de N. nycticorax de colonias reproductoras con poblaciones estables (Washington, D.C.) y en declive (Ohio). Para las poblaciones reproductoras en América del Norte, utilizamos datos de encuentro de individuos anillados para estimar el movimiento de poblaciones entre latitudes de reproducción e invernada y la fuerza de la métrica de conectividad migratoria entre latitudes. El primer seguimiento del ciclo anual completo de N. nycticorax reveló diversas estrategias de invernada, que incluyen distribuciones geográficas amplias, movimientos durante el invierno y fidelidad del sitio entre años. Encontramos que más del 80% de los individuos rastreados de las dos poblaciones reproductoras compartieron áreas de invernada similares, que incluían el sur de los Estados Unidos, Cuba, Honduras y Nicaragua. Las garzas N. nycticorax exhibió una conectividad migratoria débil entre la reproducción e invernada (MC = 0.001 ± 0.03) a lo largo de la extensión latitudinal de su área de reproducción en América del Norte, incluyendo cierto grado de migración parcial. La alta superposición en las distribuciones invernales y las reubicaciones durante el invierno de N. nycticorax rastreadas de las poblaciones reproductoras en las dos regiones, así como la débil conectividad migratoria en su área de distribución, sugieren que las condiciones localizadas durante el período invernal pueden no estar promoviendo diferentes tendencias entre las poblaciones reproductoras.
... We made transmitter harnesses from Teflon ribbon. The harness design was similar to that outlined in Buehler et al. (1995), except that we used two 45-cm strands of ribbon to form the harness. We placed the strands along the scapulae, along either side of the sternum, and behind the wings. ...
We estimated core areas and home-range sizes and evaluated sex differences in home-range size, seasonal variation in movements, and space use for breeding Common Ravens (Corvus corax) in western Marin County, California. There were no significant interannual differences in average core area or average home-range size for either sex, although there were small-scale shifts in home-range use for 67% of females and 63% of males. There was no significant difference in home-range size between the sexes. Home-range size was positively correlated with distance to food source. Ravens traveled shorter distances from the nest during the incubation + nestling stage compared to other stages of the breeding season. Core areas were centered around nest sites and food sources, with significantly aggregated locations for 83% and 100% of females in 2000 and 2001, respectively. Males were more variable in their use of space, with significantly aggregated locations for 38% and 44% of males in 2000 and 2001, respectively. Individual variation in home-range size, movements, and space use was likely due to differences in the distribution of important food sources in the area.
Diferencias Sexuales en la Utilización del Espacio en Corvus corax en el Oeste del Condado Marin, California
Resumen. Estimamos los tamaños del área núcleo y rango de hogar y evaluamos las diferencias entre sexos en el tamaño del rango de hogar, variaciones estacionales de los movimientos y utilización del espacio en Corvus corax en el oeste del condado Marin, California. No hubo diferencias interanuales significativas en el área núcleo promedio ni en el rango de hogar promedio para ninguno de los sexos, aunque para el 67% de las hembras y el 63% de los machos hubo cambios de pequeña escala en el uso del rango de hogar. No hubo diferencias significativas en el tamaño de los rangos de hogar entre sexos. El tamaño del rango de hogar estuvo positivamente correlacionado con la distancia a la fuente de alimento. Los cuervos viajaron distancias más cortas desde el nido durante los períodos de incubación y de cría de polluelos en comparación con otros períodos durante la época reproductiva. Las áreas núcleo se centraron en los sitios de nidificación y las fuentes de alimento, con posiciones significativamente agregadas para el 83% y 100% de las hembras en 2000 y 2001, respectivamente. Los machos presentaron mayor variabilidad en la utilización del espacio, con posiciones significativamente agregadas para un 38% y 44% de los machos en el 2000 y 2001, respectivamente. Las variaciones individuales en el tamaño de los ámbitos de hogar, movimientos y uso del espacio fueron probablemente dadas por las diferencias en la distribución de los recursos alimenticios importantes en el área.
... Tracked woodpeckers were targeted for mist nest captures with playback and wooden decoy. Males were colourbanded, fitted with VHF radio-backpacks (ATS, model A1250, Buehler et al. 1995) and released at the site of capture. We located individuals by using the homing technique, which consisted of locating the source of the VHF signal emitted by a transmitter attached to the dominant male woodpecker of a given family group (Soto et al. 2017). ...
Animals facing seasonal food shortage and habitat degradation may adjust their foraging behaviour to reduce intraspecific competition. In the harsh environment of the world's southernmost forests in the Magellanic sub-Antarctic ecoregion in Chile, we studied intersexual foraging differences in the largest South American woodpecker species, the Magellanic Woodpecker (Campephilus magellanicus). We assessed whether niche overlap between males and females decrease when food resources are less abundant or accessible, that is, during winter and in secondary forests, compared to summer and in old-growth forests, respectively. We analysed 421 foraging microhabitat observations from six males and six females during 2011 and 2012. As predicted, the amount of niche overlap between males and females decreased during winter, when provisioning is more difficult. During winter, males and females (i) used trees with different diameter at breast height (DBH); (ii) fed in trunk sections with different diameters; and (iii) fed at different heights on tree trunks or branches. Vertical niche partitioning between sexes was found in both old-growth and secondary forests. Such a niche partitioning during winter may be a seasonal strategy to avoid competition between sexes when prey resources are less abundant or accessible. Our results suggest that the conservation of this forest specialist, dimorphic and charismatic woodpecker species requires considering differences in habitat use between males and females.
... Transmitter application.--We applied transmitters as backpacks using a Teflon © ribbon harness (after the "Y design" in Buehler et al. 1995) modified with a leather breast-patch. To construct the harness, we threaded two lengths of ribbon through slits cut across the corners of a 13 x 19 mm leather patch. ...
We examined the effects of backpack radio transmitters on Prairie Falcon (Falco mexicanus) reproduction (percentage of occupied territories producing young and number of nestlings produced) over four years. In addition, we observed falcon aeries during brood-rearing to determine attendance at the nest and in the territory, prey delivery rates, and prey composition. We found no effect of radio tagging on Prairie Falcon productivity (nesting success and brood size) among years, although productivity varied significantly among years. The sex of the falcon tagged did not affect productivity. Radio-tagged members of pairs did not differ significantly from un-tagged members of pairs in territory attendance, nest attendance, prey delivery rates, or caching rates. Nestlings raised by radio-tagged parents attained masses similar to those reared by control parents. During low prey years, radio-tagged males brought a greater proportion of small birds and reptiles, and fewer mammals to the nest area than control males.
... We captured and then banded birds with a unique combination of color bands. Backpack radiotransmitters (Buehler et al. 1995, Vekasy et al. 1996 were also applied to at least one member of the pair (N 5 14). We made a minimum of 20 separate visits and spent a minimum of 250 observer hr at each site to trap and identify birds. ...
Point-count surveys with playback recordings have been used to estimate density and abundance
for Hawaiian Hawks (‘Io; Buteo solitarius) on Hawaii. Playbacks are necessary for effective surveys, but
attract hawks toward the observer prior to their detection. This attraction inflates estimates of density and
abundance based on distance analytical techniques. We quantified movement of radio-tagged Hawaiian
Hawks and evaluated six methods to adjust estimates to account for attraction. We evaluated methods by
comparing density estimates determined by spot mapping to adjusted point counts at two study sites (Kona
Forest, Puu Waawaa) during 1998 and 1999 on Hawaii. By spot mapping, we estimated densities of 0.59 and
0.76 hawks/km2 at the Puu Waawaa and Kona Refuge study sites, respectively. We adjusted for (1) lack of
response, (2) attraction to calls, (3) attraction and lack of response, (4) view obstruction, (5) view obstruction
and lack of response, and (6) movement prior to detection. All methods were effective in adjusting
density at the two study areas, but simply subtracting the mean distance moved from estimated distances
(attraction) provided nearly identical density estimates to spot mapping. We describe a simple computer
simulation routine to accomplish this task for future Hawaiian Hawk surveys.
... We captured and then banded birds with a unique combination of color bands. Backpack radiotransmitters (Buehler et al. 1995, Vekasy et al. 1996 were also applied to at least one member of the pair (N 5 14). We made a minimum of 20 separate visits and spent a minimum of 250 observer hr at each site to trap and identify birds. ...
Las estimaciones de la densidad y abundancia de Buteo solitarius en Hawai se han realizado utilizando reproducción de sonidos previamente grabados en conteos en puntos. La reproducción de sonidos previamente grabados es necesaria para realizar muestreos efectivos, pero atrae a las aves hacia el observador con anterioridad a su detección. Esta atracción hace que se sobrestimen la densidad y la abundancia al emplear técnicas analíticas de distancia de detección. Cuantificamos los movimientos de individuos de B. solitarius marcados con transmisores, y evaluamos seis métodos para ajustar las estimaciones considerando los sesgos de atracción. Evaluamos los métodos comparando las estimaciones de densidad determinadas por medio del mapeo de puntos de localización con estimaciones basadas en datos ajustados de conteos en puntos en dos sitios de estudio en Hawai (Bosque Kona, Puu Waawaa) durante 1998 y 1999. Mediante el mapeo de localizaciones, estimamos densidades de 0.59 y 0.76 individuos/km2 en Puu Waawaa y el Refugio Kona, respectivamente. Los ajustes se hicieron con base en (1) falta de respuesta, (2) atracción a los llamados, (3) atracción y falta de respuesta, (4) obstrucción de la vista, (5) obstrucción de la vista y falta de respuesta y (6) movimiento previo a la detección. Todos los métodos fueron efectivos para ajustar la densidad en las áreas de estudio, pero simplemente sustraer la distancia media de movimiento de las distancias estimadas (atracción) brindó estimaciones de densidad casi idénticas a las obtenidas mediante el mapeo de puntos de localización. Describimos una rutina simple de simulaciones de ordenador para cumplir esta tarea en muestreos futuros de B. solitarius. [Traducción del equipo editorial]
To provide the U.S. Fish and Wildlife Service (USFWS) with updated information on the Hawaiian hawk ('io, Buteo solitarius) for reconsideration of its current endangered status, we determined population size, distribution, habitat availability, survival, fecundity, and finite rate of increase (lambda) of 'io during 1998 and 1999 on the island of Hawaii. We estimated the total population at 1,457 +- 176.3 SE 'io. Birds were broadly distributed around the island, but highest densities were found in mature native forest with a grass understory (0.57 +- 0.12 'io/km2). We estimated that 58.7% of the island (6,144 km2) was usable habitat for 'io. Of the usable habitat, 31.8% (1,954 km2) currently is protected by state and federal forests, parks, and refuges. Based on an average density of 0.24 +- 0.08 'io/km2 in those areas, we calculated that protected areas currently support 469 'io (95% CI: 244-901). In all habitats combined, first-year and adult survival was 0.50 +- 0.10 and 0.94 +- 0.04, respectively, and fecundity was 0.23 +- 0.04 female young/breeding female. Overall, lambda was 1.03 +- 0.04. Elasticity analyses showed adult survival to be the most important parameter regulating finite growth of this population. The population appears viable based on lambda is approximately 1 and high adult survival. Additionally, substantial areas of habitat are protected, 'io appear resistant to avian diseases found on the island, no evidence exists of negative impacts from contaminants, and the birds show the ability to use human-altered landscapes and exotic prey. Because of the short study duration, relatively low population size, variance around our estimates (abundance, fecundity, survival, lambda), and environmental stochasticity, we believe that delisting to a nonthreatened status is unwarranted, However, we believe that downlisting to threatened status would be appropriate for this species, or embracing a listing as "near threatened" under the International Union for the Conservation of Nature (IUCN) Red List categories. Regardless of a change in political status, population size and especially adult survivorship should be routinely monitored.
We estimated core areas and home-range sizes and evaluated sex differences in home-range size, seasonal variation in movements, and space use for breeding Common Ravens (Corvus corax) in western Marin County, California. There were no significant interannual differences in average core area or average home-range size for either sex, although there were small-scale shifts in home-range use for 67% of females and 63% of males. There was no significant difference in home-range size between the sexes. Home-range size was positively correlated with distance to food source. Ravens traveled shorter distances from the nest during the incubation + nestling stage compared to other stages of the breeding season. Core areas were centered around nest sites and food sources, with significantly aggregated locations for 83% and 100% of females in 2000 and 2001, respectively. Males were more variable in their use of space, with significantly aggregated locations for 38% and 44% of males in 2000 and 2001, respectively. Individual variation in home-range size, movements, and space use was likely due to differences in the distribution of important food sources in the area.
Thesis (M.S.)--Humboldt State University, 2003. Includes bibliographical references (leaves 28-33).
Bald Eagles (Haliaeetus leucocephalus) were captured using a system of 4 monofilament snares fixed on a small (20-24 cm) floating fish attached by monofilament and shock cord to a free- floating (or anchored) driftwood log. When an eagle strikes the bait and begins to fly away, the snare loops close around the bird's toes as the line tightens. Resistance of the shock cord and log then slows the bird's flight until it is forced into the water. Snare sets were placed in view of perched birds and were effective at capturing specific individuals. Capture success averaged 50% of all birds that struck the bait. Floating-fish snares are useful where topographical features, eagle foraging habits, or trap fouling by non-target terrestrial species make open water sets more effective. Non-target aquatic species occasionally fouled sets. Common methods of capturing the Bald Eagle (ttaliaeetus leucocephalus) have included padded leg- hold traps, perch snares, modified bal-chatris, can- non nets and floating-fish snares (Southern 1963, 1964; Robards 1966; Frenzel and Anthony 1982; Young 1983; Harmata 1985; Hodges et al. 1987). Among techniques, padded leg-hold traps and float- ing-fish snares have become the most widely used. Leg-hold traps are useful in areas where water is frozen or otherwise unavailable and in areas where shallow water sets can be made before daylight. Floating-fish snares are often necessary where steep- gradient beaches, shoreline vegetation, visibility, or eagle foraging habits make open-water sets more effective. Southern (1963, 1964) provided the first pub- lished accounts of capture attempts using a floating- fish snare, but his efforts were unsuccessful. The late Fred C. Robards was, to our knowledge, the first to use a floating-fish snare to successfully capture Bald Eagles. In the late 1960s Robards experimented with and managed to capture several birds using a floating Herring (Clupea palladO with a single monofilament snare loop attached and reeled in and out with a fishing rod from a small boat. The floating-fish snare technique has since become widely known as the "Robards method." For years, the Robards method was spread among Bald Eagle researchers by word of mouth. More recently, Frenzel and Anthony (1982) provided a brief description of a 2-noosed variation of Robard's (unpublished) technique. We have experimented with many variations of Robard's technique, variations which, even though very subtle, can affect capture success significantly. With any animal capturing technique it is advan- tageous to 1) minimize trauma and handling time,
A concentration of bald eagles (Haliaeetus leucocephalus) along lower McDonald Creek in Glacier National Park was first recorded in November 1939, when 37 were observed (Shea 1978). On that occasion and during each subsequent autumn, bald eagles have congregated to feed on spawning kokanee salmon (Oncorhynchus nerka). Kokanee is a non-native species, first introduced in the Flathead River drainage (in which McDonald Creek occurs) in 1978. Preliminary data suggest that there may be nearly 1,000 bald eagles now stopping at the Glacier concentration annually, although maximum counts are well below this level because of a high turnover rate. The northern subspecies of the bald eagle was classified as endangered in February 1978 under the aegis of the Endangered Species Act of 1973 and subsequent amendments. This conveys a high level of responsibility upon managers of lands and waters used by bald eagles and demands a commitment to effective habitat management. The purpose of our research is to provide information essential to such management - knowledge of movement patterns, spatial and temporal distributions, numbers, and morhpology - directly benefiting not only Glacier National Park managers, but all public agencies, industrial corporations and private land owners responsible for bald eagle habitat. This report summarizes the first part of the fourth year of a study of the ecology of Bald Eagles associated with the Glacier concentration. At this writing eagles are being tracked in the western states. Most data from this autumn have not yet been analyzed.
Effects of radio packages on movements, survival, and reproductive success of 293 young blue grouse (Dendragapus obscurus) were studied on Hardwicke Island, British Columbia, during 1979-83. Similar proportions of radio-marked and nonradioed birds were sighted by census crews in the spring after banding, indicating similar rates of survival in the two groups. Survival of radio-marked birds was not influenced by date of hatch, age at capture, date of capture, body weight, transmitter weight, or ratio of transmitter weight to body weight. Radio-equipped and nonradioed grouse behaved alike upon release and made similar daily movements during the 1st 5 days after release. Nesting success, clutch size, and brood size at hatching were similar for radioed and nonradioed females. Harnesses caused deaths of four grouse directly and some feather wear after 10 months.
One hundred seventy-nine hand-reared mallards (Anas platyrhynchos) of two genetic strains were banded and released in two areas of Minnesota. One area usually had high and the other low natural productivity of waterfowl. Eighty birds were marked with miniature radio transmitters prior to release. Mortality, movements, and habitat use were determined by radio-tracking. Forty of the 56 radio-marked birds that were monitored died within 21 days of release. Mink (Mustela vison) killed 21, avian predators killed 7, and unknown mammalian predation accounted for 9 deaths. Starvation, poaching, and unknown predation were each responsible for one death. Twelve carcasses of banded birds were found. Mink predation was the cause of death in all these cases. In addition, 9 radio-marked and 16 banded birds were shot by hunters. There was no measurable difference in survival between genetic strains or sexes. Ducklings released in the area of high natural productivity had significantly (P < 0.01) lower mortality than birds released in the area of low natural productivity. This lower mortality was attributed to differences in fertility and vegetation on the two areas. No significant difference (P < 0.05) in mortality between radio-marked and control birds was noted. Most mortality occurred within a 2-week period after release. Released birds gathered in large groups. Our findings are in close agreement with previous studies and indicate low survival and a high vulnerability to the gun. Lack of wariness, tendency of birds to gather in large groups, and releases in habitat of poor quality were the main factors contributing to the low survival of the hand-reared mallards.
Survival of 39 radio-tagged Haliaeetus leucocephalus in the Chesapeake Bay region was 100% in the first year of life. Mean minimum survival per year of all eagles was 91%, mean maximum survival 98%. A deterministic life-table model predicted a finite growth rate of 5.8% per year; growth rate based on the maximum survival estimates was 16.6% per year. The breeding population actually increased 12.6% per year from 1986-1990. Intrinsic growth rate was 6.9% based on natality and minimum survival data and 19.2% based on maximum survival data. -from Authors
The estimation of survival distributions for animals which are radio-tagged is an important current problem for animal ecologists. Allowance must be made for censoring due to radio failure, radio loss, emigration from the study area and animals surviving p88l. :~the end of the study period. First we show that the Kaplan-Meier .procedure wid~ly used in medical and engineering studies can be applied to this problem. An example using some quail data is given for illustration. As radios maItunction -or are lost, new radio-tagged animals have to be added to the study. We show how this modification can easily be incorpor~.ted inf.<? the basic Kaplan-Meier procedure. Another example using quail data is used to illustrate the extension. We also show how the log rank test commonly used to compare two survival distributions can be generalized to allow for additions. Simple computer programs which can be run on a PC are available from the authors.
SUMMARY The aerodynamic drag of bird bodies was measured in a wind tunnel, with and without back-mounted dummy radio transmitters. Flight performance estimates indicate that the drag of a large transmitter can cause a substantial reduction of a migrant's range, that is, the distance it can cover in non-stop flight. The drag of the transmitter can be reduced by arranging the components in an elongated shape, so minimizing the frontal area. The addition of a rounded fairing to the front end, and a pointed fairing behind, was found to reduce the drag of the transmitter by about one- third, as compared with an unfaired rectangular box.
Summary Two Harris' hawks were trained to fly along horizontal and climbing flight paths, while carrying loads of various masses, to provide data for estimating available muscle power during short flights. The body mass of both hawks was about 920 g, and they were able to carry loads up to 630 g in horizontal flight. The rate of climb decreased with increasing all-up mass, as also did the climbing power (product of weight and rate of climb). Various assumptions about the aerody- namic power in low-speed climbs led to estimates of the maximum power output of the flight muscles ranging from 41 to 46 W. This, in turn, would imply a stress during shortening of around 210 kPa. The effects of a radio package on a bird that is raising young should be considered in relation to the food load that the forager can normally carry, rather than in relation to its body mass.
Resting metabolic rate of Golden Eagles, Bald Eagles, and Barred Owls with a tracking transmitter or an equivalent load Transmitter loads affect the flight speed and metabolism of homing pigeons
- M R Fuller
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- And G E Duke
- And K A
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Received 21 Feb. 1994; accepted 31 May 1994.
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Solar radio-transmitters on Snail Kites in Florida
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Wildlife radio tagging
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The post-fledging ecology and population dynamics of bald eagles in Maine
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eagles in Maine. Ph.D. thesis. Univ. Maine, Orono, Maine.
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