Water retention in the plumage of diving great cormorants Phalacrocorax carbo sinensis

Cormorants are assumed to have a "partially wettable" plumage as a mechanism to reduce buoyancy while swimming underwater. This assumption is mainly based on 3 observations: 1) the volume of air in the plumage of submerged carcasses is small compared to other water birds, 2) cormorants assume a "wing drying" posture when they exit the water, and 3) the feather structure of the plumage. An alternative mechanism to reduce buoyancy is to release air out of the plumage by ptilomotion without allowing water to penetrate. How wet cormorants actually get is an open issue that has important implications for the energy budget of these warm blooded aquatic predators. Here we report empirical measurements on the amount of water retained in the plumage of live great cormorant Phlacrocorax carbo sinensis during voluntary swimming and diving in an experimental design that simulates a foraging diving bout. The amount of water retained in the plumage increased as a function of time spent in water. However the birds limited their dive bouts to less than 18 minutes so that the added mass of retained water did not exceed 6% of their body mass. This maximal level of water retention is estimated to reduce the buoyancy of the dry bird by 18%. This maximal level is also similar to measurements of water retention of carcasses and suggests that measurements preformed on carcasses yield only the upper level of water absorption while live birds slow down water penetration, allowing longer periods of foraging.     

Diving in shallow water: the foraging ecology of darters (Aves: Anhingidae)

Diving birds have to overcome buoyancy, especially when diving in shallow water. Darters and anhingas (Anhingidae) are specialist shallow-water divers, with adaptations for reducing their buoyancy. Compared to closely-related cormorants (Phalacrocoracidae), darters have fully wettable plumage, smaller air sacs and denser bones. A previous study of darter diving behaviour reported no relationship between dive duration and water depth, contrary to optimal dive models. In this study I provide more extensive observations of African darters Anhinga melanogaster rufa diving in water<5 m deep at two sites. Dive duration increases with water depth at both sites, but the relationship is weak. Dives were longer than dives by cormorants in water of similar depth (max 108 s in water 2.5 m deep), with dives of up to 68 s observed in water<0.5 m deep. Initial dives in a bout were shorter than expected, possibly because their plumage was not fully saturated. Dive efficiency (dive:rest ratio) was 5–6, greater than cormorants (2.7±0.4 for 18 species) and other families of diving birds (average 0.2–4.3). Post-dive recovery periods increased with dive duration, but only slowly, resulting in a strong increase in efficiency with dive duration. All dives are likely to fall within the theoretical anaerobic dive limit. Foraging bouts were short (17.8±4.3 min) compared to cormorants, with birds spending 80±5% of time underwater. Darters take advantage of their low buoyancy to forage efficiently in shallow water, and their slow, stealthy dives are qualitatively different from those of other diving birds. However, they are forced to limit the duration of foraging bouts by increased thermoregulatory costs associated with wettable plumage.     

Body temperature and insulation in diving Great Cormorants and European Shags

1. Cormorants are typically considered as wettable diving birds with high thermoregulatory costs and are presumed to exert substantial predatory pressure on fish stocks.
2. The stomach temperatures of seven Great Cormorants and three European Shags were recorded during a total of 108 foraging trips undertaken near the Chausey Islands breeding colony (France).
3. Both species kept a constant body temperature during the dive series which lasted up to 158 min and were conducted in 12°C water. Consequently, assuming that heat loss to the water is equal to heat production in diving Great Cormorants, the minimal insulating plumage air volume was calculated to be 0·371 × 10^–3 m³ (corresponding to a 1·62-mm air layer) in males and 0·347 × 10^–3 m³ (corresponding to a 1·90-mm air layer) in females.
4. Furthermore, it is shown that plumage air volume and dive depth are the major factors influencing heat flux to the water and that the energetics of diving Great Cormorants may also vary substantially according to fat layer thickness, water temperature and body temperature. Swim speed plays only a minor role.
5. Considering these results, it is postulated that Great Cormorants may have optimized plumage air volume so as to minimize both mechanical costs (upthrust) and thermoregulatory costs of swimming in cold, shallow water.
6. Finally, body temperature patterns recorded in different cormorant species while diving are compared.     

A life in the fast lane: energetics and foraging strategies of the great cormorant

Body insulation is critically important for diving marine endotherms. However,cormorants have a wettable plumage, which leads to poor insulation. Despitethis, these birds are apparently highly successful predatorsin most aquatic ecosystems. We studied the theoretical influenceof water temperature, dive depth, foraging techniques, and preyavailability on the energetic costs of diving, prey search time,daily food intake, and survival in foraging, nonbreeding greatcormorants (Phalacrocorax carbo). Our model was based on fieldmeasurements and on data taken from the literature. Water temperatureand dive depth influenced diving costs drastically, with predicted increasesof up to 250% and 258% in males and females, respectively. Changes inwater temperature and depth conditions may lead to an increaseof daily food intake of 500-800 g in males and 440-780 g infemales. However, the model predicts that cormorant foragingparameters are most strongly influenced by prey availability,so that even limited reduction in prey density makes birds unableto balance energy needs and may thus limit their influence onprey stocks. We discuss the ramifications of these results withregard to foraging strategies, dispersal, population dynamics,and intraspecific competition in this avian predator and pointout the importance of this model species for our understandingof foraging energetics in diving endotherms.     

On a wing and a prayer: the foraging ecology of breeding Cape cormorants

The Cape cormorant Phalacrocorax capensis is unusual among cormorants in using aerial searching to locate patchily distributed pelagic schooling fish. It feeds up to 80 km offshore, often roosts at sea during the day and retains more air in its plumage and is more buoyant than most other cormorants. Despite these adaptations to its pelagic lifestyle, little is known of its foraging ecology. We measured the activity budget and diving ecology of breeding Cape cormorants. All foraging took place during the day, with 3.6 ± 1.3 foraging trips per day, each lasting 85 ± 60 min and comprising 61 ± 53 dives. Dives lasted 21.2 ± 13.9 s (maximum 70 s), attaining an average depth of 10.2 ± 6.7 m (maximum 34 m), but variability in dive depth both within and between foraging trips was considerable. The within-bout variation in dive depth was greater when making shallow dives, suggesting that pelagic prey were targeted mainly when diving to <10 m. Diving ecology and total foraging time were similar to other cormorants, but the time spent flying (122 ± 51 min day⁻¹, 14% of daylight) was greater and more variable than other species. Searching flights lasted up to 1 h, and birds made numerous short flights during foraging bouts, presumably following fast-moving schools of pelagic prey. Compared with the other main seabird predators of pelagic fish in the Benguela region, Cape gannets Morus capensis and African penguins Spheniscus demersus , Cape cormorants made shorter, more frequent foraging trips. Their foraging range while feeding small chicks was 7 ± 6 km (maximum 40 km), similar to penguins (10–20 km), but less than gannets (50–200 km). Successful breeding by large colonies depends on the reliable occurrence of pelagic fish schools within this foraging range.     

Effects of air and water temperatures on resting metabolism of auklets and other diving birds

For small aquatic endotherms, heat loss while floating on water can be a dominant energy cost, and requires accurate estimation in energetics models for different species. We measured resting metabolic rate (RMR) in air and on water for a small diving bird, the Cassin's auklet (Ptychoramphus aleuticus), and compared these results to published data for other diving birds of diverse taxa and sizes. For 8 Cassin's auklets (~165 g), the lower critical temperature was higher on water (21 °C) than in air (16 °C). Lowest values of RMR (W kg?1) averaged 19% higher on water (12.14 ± 3.14 SD) than in air (10.22 ± 1.43). At lower temperatures, RMR averaged 25% higher on water than in air, increasing with similar slope. RMR was higher on water than in air for alcids, cormorants, and small penguins but not for diving ducks, which appear exceptionally resistant to heat loss in water. Changes in RMR (W) with body mass either in air or on water were mostly linear over the 5- to 20-fold body mass ranges of alcids, diving ducks, and penguins, while cormorants showed no relationship of RMR with mass. The often large energetic effects of time spent floating on water can differ substantially among major taxa of diving birds, so that relevant estimates are critical to understanding their patterns of daily energy use.     

Behavioural strategies of cormorants (Phalacrocoracidae) foraging under challenging light conditions

Diving is indicative of foraging in cormorants (Phalacrocoracidae). We have investigated a range of parameters associated with diving in Great Cormorants Phalacrocorax carbo to provide insight into the bases of cormorant predatory strategies. We hypothesize that if vision is important in cormorant foraging behaviour, and if they are not constrained by the position of their prey in the water column, then diving behaviour will be modulated primarily in response to the diel variation in ambient light levels. Specifically, we propose that cormorants forage at shallower depths when light levels are low, and more deeply when light levels are high. We provide evidence that this is the case. We recorded the occurrence of cormorant diving behaviour using implanted data loggers and recorded ambient light levels and water temperature using leg-mounted loggers in a sample of free-living Great Cormorants in Greenland. Our results show that dives are shallower at the beginning and end of each day when light levels are lower. We suggest that these data support the hypothesis that cormorant foraging is visually-guided even though recent evidence has shown that their underwater visual acuity is poor.     

Cormorants dive through the Polar night

Most seabirds are visual hunters and are thus strongly affected by light levels. Dependence on vision should be problematic for species wintering at high latitudes, as they face very low light levels for extended periods during the Polar night. We examined the foraging rhythms of male great cormorants (Phalacrocorax carbo) wintering north of the Polar circle in West Greenland, conducting the first year-round recordings of the diving activity in a seabird wintering at high latitudes. Dive depth data revealed that birds dived every day during the Arctic winter and did not adjust their foraging rhythms to varying day length. Therefore, a significant proportion of the dive bouts were conducted in the dark (less than 1 lux) during the Polar night. Our study underlines the stunning adaptability of great cormorants and raises questions about the capacity of diving birds to use non-visual cues to target fish.     

Leg-attached data loggers do not modify the diving performances of a foot-propelled seabird

Global location sensors (GLS) are increasingly being used to determine animal position at sea. Their small size and weight means that they can be attached to the leg of volant birds with supposedly little impact on the flight ability. However, very few studies have investigated the impact that foot-attached devices may have on the diving ability of foot-propelled seabirds. We compared the diving activity of two groups of free-ranging great cormorants Phalacrocorax carbo carbo , both groups carrying identical time-depth recorders attached to the tail, and one group also having leg-attached GLS. Our results showed that there were no differences between the two groups in any of the diving parameters investigated, at least over the short term. Caution should be exercised when extrapolating to other species, especially those smaller than great cormorants, and also when deploying GLS over longer periods.     

Pedestrian locomotion energetics and gait characteristics of a diving bird, the great cormorant, Phalacrocorax carbo

Great cormorants Phalacrocorax carbo are foot propelled diving birds that seem poorly suited to locomotion on land. They have relatively short legs, which are presumably adapted for the generation of high forces during the power stroke of aquatic locomotion, and walk with a pronounced "clumsy waddle". We hypothesise (1) that the speed, independent minimum cost of locomotion (C min, ml O2 m(-1)) will be high for cormorants during treadmill exercise, and (2) that cormorants will have a relatively limited speed range in comparison to more cursorial birds. We measured the rate of oxygen consumption (V02) of cormorants during pedestrian locomotion on a treadmill, and filmed them to determine duty factor (the fraction of stride period that the foot is in contact with the ground), foot contact time (tc), stride frequency (f), swing phase duration and stride length. C min was 2.1-fold higher than that predicted by their body mass and phylogenetic position, but was not significantly different from the C min of runners (Galliformes and Struthioniformes). The extrapolated gamma-intercept of the relationship between V02 and speed was 1.9-fold higher than that predicted by allometry. Again, cormorants were not significantly different from runners. Contrary to our hypothesis, we therefore conclude that cormorants do not have high pedestrian transport costs. Cormorants were observed to use a grounded gait with two double support phases at all speeds measured, and showed an apparent gait transition between 0.17 and 0.25 m s(-1). This transition occurs at a Froude number between 0.016 and 0.037, which is lower than the value of approximately 0.5 observed for many other species. However, despite the use of a limited speed range, and a gait transition at relatively low speed, we conclude that the pedestrian locomotion of these foot propelled diving birds is otherwise generally similar to that of cursorial birds at comparable relative velocities.     

Sexual differences in the diet of great cormorants <Emphasis Type="Italic">Phalacrocorax carbo sinensis</Emphasis> wintering in Greece

Sexual differences in the diet of the great cormorant, Phalacrocorax carbo sinensis, were studied in four Greek wintering areas, the Amvrakikos Gulf, the Axios and Evros Deltas and the Messolonghi Lagoon, through the analysis of stomach contents. Great cormorants are birds sexually dimorphic in size, with males being generally larger than females. Although similar prey species were found in the stomachs of both sexes in all the studied areas, significant differences were observed with respect to the proportion of species taken. Male birds ate higher proportions of large fish species such as grey mullets, European sea bass, Dicentrarchus labrax, and Prussian carp, Carassius gibelio, while female birds took higher proportions of smaller species such as big-scale sand smelt, Atherina boyeri, and black goby, Gobius niger. As a consequence, male great cormorants were found to feed on significantly larger prey than did females by means of fish standard length and body mass. There was no significant difference between the sexes in the mass of food found in stomachs.     

THE LITTLE SWIFT AND OTHERS AT KASAMA

Rijke, A. M., Jesser, W. A. &; Mahoney, S. A. 1989. Plumage wettability of the African Darter Anhinga melanogaster compared with the Double-crested Cormorant Phalacrocarax auritus. Ostrich 60:128-132.

Darters emerge from water “dripping wet” but are able to become airborne without delay. Their plumage is, on the whole, three times more wettable than that of cormorants. We investigated the microscopic structure and resistance to water penetration of the body, wing and tail feathers of the African Darter, Anhinga melanogaster.

The results show values of the structural parameter (r + d)/r for body feathers in the range of 9 to 12, whereas for rectrices, primaries, secondaries and tertiaries, a range of 2 to 3 was observed, with barbules measuring 2 to 3. Penetration pressures measure zero to 1 cm water head for the body feathers and 6 to 15 cm for the wing and tail feathers. These findings suggest that on submersion, the body feathers wet out entirely but wing and tail feathers resist becoming waterlogged which may reduce buoyancy when stalking prey underwater and permit the darter to take to the air immediately after a dive. The results have been compared with those of similar measurements on cormorant feathers, which underscore the dual nature of the darter plumage in terms of water repellency and resistance to water penetration.     

Foraging by deep-diving birds is not constrained by an aerobic diving limit: a model of avian depth-dependent diving metabolic rate

The theoretical aerobic diving limit (tADL) specifies the duration of a dive after which oxygen reserves available for diving are depleted. The tADL has been calculated by dividing the available oxygen stores by the diving metabolic rate (DMR). Contrary to diving mammals, most diving birds examined to date exceed the tADL by a large margin. This discrepancy between observation and theory has engendered two alternative explanations suggesting that dive duration is extended either anaerobically or by depressing aerobic metabolism. Current formulations of tADL uncritically assume that DMR is independent of depth. However, diving birds differ from other vertebrate divers by having a larger respiratory system volume and by retaining air in their plumage while diving, thereby elevating buoyancy. Because air compresses with depth, diving power requirement decreases with depth. Following this principle, we modeled DMR to depth for Adelie and little penguins and reformulated the tADL accordingly. The model's results suggest that < approximately 5% of natural dives by Adelie penguins exceed the reformulated tADL(d), or maximal aerobic depth, and none in the more buoyant little penguin. These data suggest that, for both small and large species, deep diving birds rarely if ever exceed tADL(d).     

Buoyancy under Control: Underwater Locomotor Performance in a Deep Diving Seabird Suggests Respiratory Strategies for Reducing Foraging Effort

Background

Because they have air stored in many body compartments, diving seabirds are expected to exhibit efficient behavioural strategies for reducing costs related to buoyancy control. We study the underwater locomotor activity of a deep-diving species from the Cormorant family (Kerguelen shag) and report locomotor adjustments to the change of buoyancy with depth.

Methodology/Principal Findings

Using accelerometers, we show that during both the descent and ascent phases of dives, shags modelled their acceleration and stroking activity on the natural variation of buoyancy with depth. For example, during the descent phase, birds increased swim speed with depth. But in parallel, and with a decay constant similar to the one in the equation explaining the decrease of buoyancy with depth, they decreased foot-stroke frequency exponentially, a behaviour that enables birds to reduce oxygen consumption. During ascent, birds also reduced locomotor cost by ascending passively. We considered the depth at which they started gliding as a proxy to their depth of neutral buoyancy. This depth increased with maximum dive depth. As an explanation for this, we propose that shags adjust their buoyancy to depth by varying the amount of respiratory air they dive with.

Conclusions/Significance

Calculations based on known values of stored body oxygen volumes and on deep-diving metabolic rates in avian divers suggest that the variations of volume of respiratory oxygen associated with a respiration mediated buoyancy control only influence aerobic dive duration moderately. Therefore, we propose that an advantage in cormorants - as in other families of diving seabirds - of respiratory air volume adjustment upon diving could be related less to increasing time of submergence, through an increased volume of body oxygen stores, than to reducing the locomotor costs of buoyancy control.     

Using species distribution models to define nesting habitat of the eastern metapopulation of double‐crested cormorants

When organisms with similar phenotypes have conflicting management and conservation initiatives, approaches are needed to differentiate among subpopulations or discrete groups. For example, the eastern metapopulation of the double‐crested cormorant (Phalacrocorax auritus) has a migratory phenotype that is culled because they are viewed as a threat to commercial and natural resources, whereas resident birds are targeted for conservation. Understanding the distinct breeding habitats of resident versus migratory cormorants would aid in identification and management decisions. Here, we use species distribution models (SDM: Maxent) of cormorant nesting habitat to examine the eastern P. auritus metapopulation and the predicted breeding sites of its phenotypes. We then estimate the phenotypic identity of breeding colonies of cormorants where management plans are being developed. We transferred SDMs trained on data from resident bird colonies in Florida and migratory bird colonies in Minnesota to South Carolina in an effort to identify the phenotype of breeding cormorants there based on the local landscape characteristics. Nesting habitat characteristics of cormorant colonies in South Carolina more closely resembled those of the Florida phenotype than those of birds of the Minnesota phenotype. The presence of the resident phenotype in summer suggests that migratory and resident cormorants will co‐occur in South Carolina in winter. Thus, there is an opportunity for separate management strategies for the two phenotypes in that state. We found differences in nesting habitat characteristics that could be used to refine management strategies and reduce human conflicts with abundant winter migrants and, at the same time, conserve less common colonies of resident cormorants. The models we use here show potential for advancing the study of geographically overlapping phenotypes with differing conservation and management priorities.     

Moving towards acceleration for estimates of activity-specific metabolic rate in free-living animals: the case of the cormorant

1. Time and energy are key currencies in animal ecology, and judicious management of these is a primary focus for natural selection. At present, however, there are only two main methods for estimation of rate of energy expenditure in the field, heart rate and doubly labelled water, both of which have been used with success; but both also have their limitations. 2. The deployment of data loggers that measure acceleration is emerging as a powerful tool for quantifying the behaviour of free-living animals. Given that animal movement requires the use of energy, the accelerometry technique potentially has application in the quantification of rate of energy expenditure during activity. 3. In the present study, we test the hypothesis that acceleration can serve as a proxy for rate of energy expenditure in free-living animals. We measured rate of energy expenditure as rates of O2 consumption (VO2) and CO2 production (VCO2) in great cormorants (Phalacrocorax carbo) at rest and during pedestrian exercise. VO2 and VCO2 were then related to overall dynamic body acceleration (ODBA) measured with an externally attached three-axis accelerometer. 4. Both VO2 and VCO2 were significantly positively associated with ODBA in great cormorants. This suggests that accelerometric measurements of ODBA can be used to estimate VO2 and VCO2 and, with some additional assumptions regarding metabolic substrate use and the energy equivalence of O2 and CO2, that ODBA can be used to estimate the activity specific rate of energy expenditure of free-living cormorants. 5. To verify that the approach identifies expected trends in from situations with variable power requirements, we measured ODBA in free-living imperial cormorants (Phalacrocorax atriceps) during foraging trips. We compared ODBA during return and outward foraging flights, when birds are expected to be laden and not laden with captured fish, respectively. We also examined changes in ODBA during the descent phase of diving, when power requirements are predicted to decrease with depth due to changes in buoyancy associated with compression of plumage and respiratory air. 6. In free-living imperial cormorants, ODBA, and hence estimated VO2, was higher during the return flight of a foraging bout, and decreased with depth during the descent phase of a dive, supporting the use of accelerometry for the determination of activity-specific rate of energy expenditure.     

Parasite assemblages of Double-crested Cormorants as indicators of host populations and migration behavior

The Double-crested Cormorant (Phalacrocorax auritus) is culled in many states because of the real and presumed damages it inflicts on farmed and recreational fisheries and other ecosystem services. Resident cormorant colonies breeding in the southeastern United States are protected in some areas, so it is important to distinguish these from co-occurring but unprotected migratory cormorants. Migratory P. auritus are likely to contain helminthic parasite communities that differ from those of non-migratory, resident birds, because they will encounter a wider variety of habitats and intermediate host communities during migrations. Here, we document five distinct assemblages of helminth parasites collected from 218 P. auritus culled from 11 sites in Alabama, Minnesota, Mississippi, and Vermont. The assemblages of P. auritus parasites are distinct among many sampling locations and can be used to correctly predict where a host cormorant has been feeding. We provide evidence for mixing of cormorants at a regional scale using discriminant analysis, which suggests there is a single population of migratory cormorants. Furthermore, our models strongly differentiate between migratory and resident P. auritus in the southeastern United States. In conjunction with species-by species latitudinal and longitudinal trends, our models could serve as effective tools for managers interested in both the population control of migratory cormorants and the conservation of non-migratory, resident birds. Finally, parasite counts per host are notoriously variable with many zeros and a few large numbers, leading many researchers to use simple prevalence in their analyses. We show that an intermediate level of data resolution, using species occurrence ranks within individual hosts, behaves well statistically and provides the greatest discrimination among distinct host groupings.     

Geographic variation in the plumage coloration of willow flycatchers Empidonax traillii

The ability to identify distinct taxonomic groups of birds (species, subspecies, geographic races) can advance ecological research efforts by determining connectivity between the non‐breeding and breeding grounds for migrant species, identifying the origin of migrants, and helping to refine boundaries between subspecies or geographic races. Multiple methods are available to identify taxonomic groups (e.g., morphology, genetics), and one that has played an important role for avian taxonomists over the years is plumage coloration. With the advent of electronic devices that can quickly and accurately quantify plumage coloration, the potential of using coloration as an identifier for distinct taxonomic groups, even when differences are subtle, becomes possible. In this study, we evaluated the degree to which plumage coloration differs among the four subspecies of the willow flycatcher Empidonax traillii, evaluated sources of variation, and considered the utility of plumage coloration to assign subspecies membership for individuals of unknown origin. We used a colorimeter to measure plumage coloration of 374 adult willow flycatchers from 29 locations across their breeding range in 2004 and 2005. We found strong statistical differences among the mean plumage coloration values of the four subspecies; however, while individuals tended to group around their respective subspecies’ mean color value, the dispersion of individuals around such means overlapped. Mean color values for each breeding site of the three western subspecies clustered together, but the eastern subspecies’ color values were dispersed among the other subspecies, rather than distinctly clustered. Additionally, sites along boundaries showed evidence of intergradation and intermediate coloration patterns. We evaluated the predictive power of colorimeter measurements on flycatchers by constructing a canonical discriminant model to predict subspecies origin of migrants passing through the southwestern U.S. Considering only western subspecies, we found that individuals can be assigned with reasonable certainty. Applying the model to migrants sampled along the Colorado River in Mexico and the U.S. suggests different migration patterns for the three western subspecies. We believe that the use of plumage coloration, as measured by electronic devices, can provide a powerful tool to look at ecological questions in a wide range of avian species.     

Foraging energetics of arctic cormorants and the evolution of diving birds

Efficient body insulation is assumed to have enabled birds and mammals to colonize polar aquatic ecosystems. We challenge this concept by comparing the bioenergetics of cormorants ( Phalacrocorax carbo ) living in temperate and arctic conditions. We show that although these birds have limited insulation, they maintain high body temperature (42.3 °C) when diving in cold water (1–10 °C). Their energy demand at these times is extremely high (up to 60 W kg⁻¹). Free-living cormorants wintering in Greenland (water temperature −1 °C) profoundly alter their foraging activity, thus minimizing time spent in water and the associated high thermoregulatory costs. They then meet their daily food demand within a single intense dive bout (lasting 9 min on average). Their substantial energy requirements are balanced by the highest predatory efficiency so far recorded for aquatic predators. We postulate that similar behavioural patterns allowed early diving birds (Cretaceous) to colonize cold coastal areas before they evolved efficient insulation.     

Hematology, plasma chemistry, and serology of the flightless cormorant (Phalacrocorax harrisi) in the Galapagos Islands, Ecuador

The flightless cormorant (Phalacrocorax harrisi) is an endemic species of the Galápagos Islands, Ecuador. Health studies of the species have not previously been conducted. In August 2003, baseline samples were collected from flightless cormorant colonies on the islands of Isabela and Fernandina. Seventy-six birds, from nestlings to adults, were evaluated. Genetic sexing of 70 cormorants revealed 37 females and 33 males. Hematology assessment consisted of packed cell volume (n=19), leukograms (n=69), and blood smear evaluation (n=69). Microscopic evaluation of blood smears revealed microfilaria in 33% (23/69) of the cormorants. Plasma chemistries were performed on 46 cormorants. There was no significant difference in chemistry values or complete blood counts between male and female cormorants or between age groups. Based on a serologic survey to assess exposure to avian pathogens, birds (n=69) were seronegative for West Nile virus, avian paramyxovirus type 1 (Newcastle disease virus), avian paramyxovirus types 2 and 3, avian influenza, infectious bursal disease, infectious bronchitis, Marek's disease (herpes), reovirus, avian encephalomyelitis, and avian adenovirus type 2. Antibodies to avian adenovirus type 1 and Chlamydophila psittaci were found in 31% (21/68) and 11% (7/65) of flightless cormorants respectively. Chlamydophila psittaci was detected via polymerase chain reaction in 6% (2/33) of the cormorants. The overall negative serologic findings of this research suggest that the flightless cormorant is an immunologically na?ve species, which may have a reduced capacity to cope with the introduction of novel pathogens.