Ornithological Monographs Volume (2006), No. 60, 86–97 © The American Ornithologists’ Union, 2006. Printed in USA.
CHAPTER 6
HEALTH ASSESSMENT OF SEABIRDS ON ISLA GENOVESA, GALÁPAGOS ISLANDS L R. P ,1,2,4 N K. W ,3 J M ,1,3 K P. H ,3 P G. P 1,3 1Saint Louis Zoo, 1 Government Drive, St. Louis, Missouri 63110, USA; 2College of Veterinary Medicine, University of Missouri-Columbia, 203 Veterinary Medicine Building, Columbia, Missouri 65211, USA; and 3Department of Biology, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, Missouri 63121, USA
A .—A multispecies colony of seabirds was studied on the island of Genovesa, in the northern part of the Galápagos archipelago, Ecuador, in 2003, to establish baseline health parameters and to test specifi cally for Chlamydophila psi aci, known to exist elsewhere in the archipelago. Twenty-three Red-footed Boobies (Sula sula), 24 Great Frigatebirds (Fregata minor), 25 Nazca Boobies (S. granti), and 19 Swallow-tailed Gulls (Creagrus furcatus) were hand-restrained for venipuncture and collection of lacrimo-choanal-cloacal combination swabs. White blood cell (WBC) counts, diff erentials, and packed cell volumes were obtained and plasma chemistry analyses performed on the blood samples. Presence–absence and parasitemias of circulating hemoparasites were determined by microscopic evaluation of peripheral blood smears. Haemoproteus-like hemoparasites were found in three of the seabird species sampled. Prevalences were 29.2% (7 of 24) in Great Frigatebirds, 15.8% (3 of 19) in Swallow-tailed Gulls, and 8.7% (2 of 23) in Red-footed Boobies; none of the Nazca Boobies were infected. Parasitemia levels were relatively low within each of the infected species. Individual Great Frigatebirds with Haemoproteus infections also exhibited signifi cantly higher heterophil-to-lymphocyte concentration ratios than birds not infected with Haemoproteus, an indication that birds infected with Haemoproteus were also physiologically stressed or, alternatively, that they were actively fi ghting the infection. Haemoproteus prevalences within Great Frigatebirds on Genovesa were not signifi cantly diff erent from those previously reported from conspecifi c hosts in the Hawaiian Islands. To compare seabird hemoparasite data with those for a sympatric terrestrial species, Galapagos Doves (Zenaida galapagoensis) were sampled on Genovesa in 2004 and screened for Haemoproteus previously reported in Galapagos Doves on other islands. Prevalence in this terrestrial endemic was high (42.3%; 11 of 26), and several birds exhibited relatively high parasitemia levels. Chlamydophila psi aci was not found in any birds by either serology or antigen detection methods. Received 29 August 2005, accepted 8 September 2005.
R .—Estudiamos una colonia multiespecífi ca de aves marinas en la isla de Genovesa, en la zona norte del archipiélago de las Galápagos en Ecuador, en el año 2003, para determinar parámetros de salud básicos y probar particularmente por la presencia de Chlamydophyla psi aci, de la cual se sabe su existencia en el resto del archipiélago. Se tomaron muestras de sangre y de exudados combinados cloacales y lagrimo-coanales de 23 Sula sula, 24 Fregata minor, 25 Sula granti y 19 Creagrus furcatus. De las muestras de sangre, se obtuvieron conteos de glóbulos blancos, diferenciales y volúmenes celulares empaquetados, además de realizar análisis químicos del plasma. La presencia-ausencia y parasitemias de hemoparásitos circulantes fueron determinadas por medio de evaluaciones microscópicas de frotis de sangre periférica. Hemoparásitos parecidos a Haemoproteus fueron encontrados en tres de las especies de aves marinas muestreadas. Las frecuencias de la presencia de
4Present address: Department of Animal Health, Smithsonian National Zoological Park, 3001 Connecticut Avenue NW, Washington, D.C. 20008, USA. E-mail: [email protected] 86 GALÁPAGOS SEABIRD HEALTH SURVEY 87
hemoparásitos fue de 29.2% (7 de 24) en Fregata minor, 15.8% (3 de 19) en Creagrus furcatus y 8.7% (2 de 23) en Sula sula; ningún individuo de Sula granti estuvo infectado. Los niveles de parasitemia fueron relativamente bajos en cada una de las especies infectadas. Individuos de Fregata minor infectados con Haemoproteus también mostraron proporciones signifi cativamente altas en concentraciones de heterofi l a linfocitos en comparación con las aves no infectadas, lo que indica que las aves infectadas con Haemoproteus también estuvieron estresadas fi siológicamente o también pudieron estar luchando activamente la infección. Las frecuencias de Haemoproteus en individuos de Fregata minor en la isla de Genovesa no fueron signifi cativamente diferentes de las frecuencias previamente registradas en hospederos con específi cos en las islas Hawaianas. Para comparar la información de la presencia de Hemoparásitos en aves marinas con datos de especies terrestres simpáticas, se muestrearon individuos de Zenaida galapagoensis en la isla de Genovesa en el ano del 2004 y se determino la presencia de Haemoproteus, la cual había sido reportada previamente en individuos de Zenaida galapagoensis provenientes de otras islas. La frecuencia en esta especie terrestre endémica fue alta (42.3%; 11 de 26) y algunas aves presentaron niveles de parasitemia relativamente altos. Chlamydophyla psi aci no se encontró en ninguna de las aves cuando se utilizaron métodos de detección serológicos o de antígeno.
T G u l I are located on the Island populations may be particularly equator in the Pacifi c Ocean, ~1,000 km west of susceptible to new pathogens, because they mainland Ecuador in South America. They have have been exposed to fewer pathogens than been inhabited by humans for less than two mainland populations (Lewis 1968a, b; Dobson centuries, and their biodiversity remains largely 1988; Goüy de Bellocq et al. 2002). Colonizers intact, with only ~5% of species having been lost from the mainland will not represent all the (Gibbs et al. 1999); all the 28 breeding land-bird parasites found in their population of origin species, 26 of which are endemic, remain. High (Dobson and May 1986). Populations may grow endemism extends to seabirds, despite the huge quickly in the absence of pathogens and selec- individual ranges of some members of this tion for resistance is relaxed, facilitating the group (Dearborn et al. 2003). Nineteen seabird invasion of pathogens arriving later (Dobson species nest in the Galápagos Islands, including 1988). To illustrate using the example of four endemic species and six endemic subspe- Hawaiian songbirds, some Hawaiian endemic cies (Harris 1984). birds had higher Plasmodium parasitemia lev- In 1959, 90% of the area of the archipelago was els, higher pox prevalence, and heavier infec- set aside as a national park. However, the resi- tions than introduced birds (van Riper et al. dent human population has grown rapidly, and 1986, 2002). exotics are continually being introduced despite Concerns over the status of native avian increasing eff orts to exclude them. The Charles populations in archipelagos and the eff ects of Darwin Research Station and the Galápagos introduced diseases have been the impetus National Park are concerned about the intro- for an active health-surveillance project in the duction of avian diseases that could result in Galápagos Islands (Miller et al. 2002, Wikelski extinctions of Galápagos avifauna comparable et al. 2004). Health surveys of Galápagos birds to extinctions in Hawaii (Wikelski et al. 2004). have found a number of pathogens in domestic Disease has been implicated as a major factor in chickens (Go denker et al. 2005). Tests have the population declines and extinctions in the shown clearly that the Avipoxvirus in the chick- endemic Hawaiian avifauna (Warner 1968; van ens is a diff erent virus than the two canarypox- Riper et al. 1986, 2002), which now comprises like Avipoxvirus strains infecting the endemic less than half the species present at Polynesian landbirds (Thiel et al. 2005). Studies aimed at se lement. Avian pox (Avipoxvirus spp.) and seeing whether other pathogens are transfer- avian malaria (Plasmodium spp.) have been ring from chickens to endemics are underway. implicated as the major pathogens contributing General health surveys conducted on the Waved to this wave of Hawaiian extinctions beginning Albatross (Phoebastria irrorata) established base- in the mid-1800s (van Riper and Sco 2001, van line values for a generally healthy population Riper et al. 2002). (Padilla et al. 2003). A four-island comparison of 88 ORNITHOLOGICAL MONOGRAPHS NO. 60 the introduced Rock Pigeon (Columba livia) and parasites known to exist on the archipelago and the only endemic dove, the Galapagos Dove in seabirds elsewhere. (Zenaida galapagoensis), revealed no evidence of transmission of pathogens in either direction, M M despite the occurrence of Trichomonas gallinae in Rock Pigeons on San Cristobal, Chlamydophila Between 11 and 15 July 2003, 93 seabirds from psi aci in Galapagos Doves on Española, and a multispecies colony were sampled on Darwin Bay, on the southern part of Genovesa (00°19’N, the near-ubiquitous presence of a Haemoproteus- 89°57’W), Galápagos Islands, Ecuador. Procedures like blood parasite in the Galapagos Doves on were conducted in accordance with Saint Louis Zoo every island sampled. Interestingly, the two institutional animal care and use commi ee stan- single cases of interspecifi c parasite transmis- dards. Individuals included 24 Great Frigatebirds sion found thus far involved prey-to-predator (Fregata minor), 23 Red-footed Boobies (Sula sula), transmission of relatively benign chewing 25 Nazca Boobies (S. granti), and 20 Swallow-tailed lice (Phthiraptera: Ischnocera). Louse species Gulls (Creagrus fulcatus). In addition, we sampled one typically found only on Galapagos Doves (i.e. Yellow-crowned Night Heron (Nyctanassa violacea), Columbicola spp., Physconelloides spp.) and intro- two Short-eared Owls (Asio fl ammeus galapagoensis), duced goats (i.e. Bovicola spp.) were found as and three Galapagos Doves, all of which were fre- quently observed foraging within the colony. Lava “stragglers” on Galapagos Hawks (Buteo galapa- Gulls (Larus fuliginosus) were also seen occasionally goensis), to which they dispersed during preda- in this colony, but were not sampled. The colony tion events (Whiteman et al. 2004). However, it was chosen on the basis of size, species diversity, was the presence of C. psi aci on Española that and accessibility, and deemed representative of prompted this survey of seabirds on Genovesa. other multispecies colonies on this island. This area Chlamydophila psi aci can spread rapidly as an is frequently monitored by Galápagos National Park epizootic agent in dense bird colonies (Franson personnel, and no historical mass mortalities have 1999), and the colonial breeding habit is associ- been documented. Seabirds were hand captured ated with higher rates of parasitism (Tella 2002). while resting or standing on the ground. Owls and Few islands rival the number and density of doves were captured with hand-nets. Each bird was marked with a single permanent-marker dot on either seabirds nesting on the island of Genovesa, and the right leg or the ventral aspect of the beak to avoid we designed this survey specifi cally to test for repeated sampling. In 2004, 30 additional Galapagos the presence of C. psi aci, while gathering gen- Doves were sampled on the same site. eral health baseline data. Blood was collected from the ulnar vein, and birds The colonial breeding habits and limited were inspected for hemostasis before being returned geographic distribution of most seabirds are to the capture site. Microhematocrit tubes were fi lled, believed to make them vulnerable to mass and fresh blood smears were prepared. The remain- mortality events (Warham 1996), including ing blood was preserved in lithium heparin blood- infectious disease epizootics and environmen- collection tubes. Blood smears were fi xed in ethanol. tal disasters. Health studies on free-ranging Blood was also preserved in a lysis buff er (Longmire et al. 1988) for molecular sexing (as described by island-nesting populations of seabirds are lim- Fridolfsson and Ellegren 1999) and future genetic ited, and few species-specifi c reference ranges and population studies. Microhematocrit tubes were are available (Work 1996, 1999). Establishing centrifuged (using Mobilespin Model 128; Vulcon reference parameters from free-ranging Technologies, Grandview, Missouri), and packed cell animals is essential to conservation eff orts, volumes (PCV) were measured. Heparinized plasma se ing a baseline for recognition of health- was separated into nalgene cryotubes (Nalge Nunc related threats to a population (Spalding and International, Rochester, New York) and stored in Forrester 1993). Monitoring pelagic seabirds liquid nitrogen until further analysis. Blood smears has also been suggested as a way of assess- were stained with a modifi ed Wright-Giemsa stain ing the overall health of marine ecosystems (JorVet Dip-Quick; Jorgensen Laboratories, Loveland, Colorado) before being individually examined for (Uhart et al. 2003). The purpose of the present presence of hemoparasites. Blood smears were study was to establish species-specifi c baseline assessed for hemoparasite presence by searching health parameters for a multispecies colony of 200 oil-immersion fi elds at 100× magnifi cation. seabirds from Genovesa, an island in the north- Parasitemias (infection intensities) were recorded as eastern part of the Galapagos archipelago, and the total number of infected erythrocytes observed to test them specifi cally for C. psi aci and blood during the search of 200 oil-immersion fi elds. An GALÁPAGOS SEABIRD HEALTH SURVEY 89 estimated leukocyte count was obtained as described R by Fudge (2000). Diff erential white-blood-cell (WBC) counts were performed by counting 100 leukocytes Screening of blood smears revealed cir- under oil immersion. Within Great Frigatebirds, culating hemoparasites in three of the four diff erential WBC counts were transformed into con- seabirds examined, with Great Frigatebirds centrations by multiplying the estimated total WBC exhibiting the highest prevalence (29.2%; 7 of × –1 values (WBC 1,000 µL ) with the diff erential value, 24), followed by Swallow-Tailed Gulls (15.8%; the product of which was then divided by 100. These 3 of 19), and Red-Footed Boobies (8.7%; 2 of values (in units of 1,000 µL–1 for heterophils and lymphocytes) were then used to calculate heterophil- 23); none were seen in Nazca Boobies (0 of 25; to-lymphocyte ratios for each Great Frigatebird from Table 1 summarizes the hematology values and which both estimated WBC concentrations and diff er- hemoparasite distribution data). All circulating ential data were available (n = 16). Because heterophil- hemoparasites were morphologically consis- to-lymphocyte concentration ratios were not normally tent with Haemoproteus-like organisms (Fig. 1). distributed (based on a one-sample Kolmogorov- Haemoproteus parasites were confi rmed in one of Smirnov test), a Mann-Whitney U test was used to the three Galapagos Doves tested in 2003 and in compare concentration ratios between birds infected 11 of 26 (42.3%) of those examined in 2004, but and uninfected with Haemoproteus. Plasma remained not in the single Yellow-crowned Night Heron, frozen until shipped for C. psi aci serology testing by nor in the Short-eared Owls. Haemoproteus prev- elementary body agglutination at the Texas Veterinary Medical Diagnostic Laboratory (College Station, alence was not signifi cantly diff erent between Texas) and for plasma chemistry testing at a com- sexes within species or among individual spe- mercial veterinary laboratory (AVL Veterinary Clinical cies. Mean parasitemias (infection intensities) Laboratory, St. Louis, Missouri), using the ACE clini- were low in all three positive seabirds, but rela- cal chemistry analyzer system (Alfa Wasserman, West tively high in Galapagos Doves in both 2003 and Caldwell, New Jersey). 2004. We then compared prevalences within Sterile Dacron tip applicators were used to col- Great Frigatebirds sampled in the present study lect combination swabs of the conjunctiva, choana, (29.2%; 7 of 24) to those published by Work and and cloaca, and were subsequently frozen in nalgene Rameyer (1996) from conspecifi c hosts sampled cryotubes with no preservatives. Swabs were submit- within another Pacifi c Island oceanic archipel- ted to the Infectious Diseases Laboratory, University of Georgia-College of Veterinary Medicine, Athens, ago, Laysan and Tern Islands (35.6%; 32 of 90) Georgia, for C. psi aci antigen detection by poly- in Hawaii, and found no signifi cant diff erences merase chain reaction (PCR). in Haemoproteus prevalence between the two Results were analyzed using commercial sta- populations (P > 0.05). tistical soV ware packages (NCSS, Kaysville, Utah; Table 2 summarizes plasma-chemistry values SPSS, version 13.0, Chicago, Illinois). Data were for the four seabird species sampled. No evi- tested for normality using a Shapiro-Wilk W test or dence of C. psi aci was found by either plasma a one-sample Kolmogorov-Smirnov test, and Mann- serology or PCR of swabs in any of the birds Whitney U tests were used to compare groups if the tested. Swallow-Tailed Gulls had consistently data were not normally distributed. QUANTITATIVE lower total WBC counts than the other species PARASITOLOGY, version 2.0 (Reiczigel and Rózsa 2001), which used distribution-free statistical tests sampled. We compared the plasma-chemistry specifi cally designed for comparative parasitology, values between hemoparasitized and non- was used to compare Haemoproteus prevalences hemoparasitized birds and found no diff er- and intensities among seabirds and within species, ences between them. Across seabird species, between sexes and age classes. This program was hemoparasitized birds had slightly lower WBC also used to calculate parasite distributions within counts than nonhemoparasitized birds (WBC = species. Because 13 plasma-chemistry parameters 9.0 ± 5.3 × 103 µL–1 vs. 8.2 ± 4.1 × 103 µL–1; U = and WBC count were compared for each subset of 531, P = 0.01, n = 91), but this diff erence was not the data, a Bonferroni-corrected P value (0.05 of 14 = signifi cant when Bonferroni correction was 0.004) was used to establish statistical signifi cance. No applied. Male and female birds did not diff er Bonferroni correction was performed on the one data set (Great Frigatebird) used to compare heterophil- in occurrence of hemoparasitism, total WBC to-lymphocyte concentration ratios between birds counts, or PCV values. However, heterophil-to- infected and uninfected with Haemoproteus, given that lymphocyte concentration ratios were signifi - the relationship between variables was hypothesized cantly higher for hemoparasite-infected than for a priori. noninfected Great Frigatebirds (Fig. 2; U = 9, P = 90 ORNITHOLOGICAL MONOGRAPHS NO. 60 var/mean ratio var/mean b gos Islands. mean intensity spp. from four seabirds sampled in 2003 a Haemoproteus Haemoproteus Haemoproteus Haemoproteus Haemoproteus Haemoproteus ) ) ) 14 (15.8%) 24 (0%) 18 (8.7%) 16 (29.2%) (1–2) ) = 18 (42.3%) (1–270) n = n = n = n = n ) Sula sula S. granti Fregata minor Creagrus furcatus 14 24 18 16 = 18 Zenaida galapagoensis n = n = n = n = n ( c Nazca Booby ( Red Footed Booby ( 14 24 18 16 with an infection intensity of 8. Great Frigatebird ( = 18 n = n = n = n = n Swallow-Tailed Gull ( Swallow-Tailed Galápagos Dove Haemoproteus -like organisms on smear examination. 14 24 18 16 = 18 n = n = n = n n = Haemoproteus 14 24 18 16 = 18 n = n = n = n = (%) (%) (%) prevalence (%) (%) 1,000 Heterophils Lymphocytes Basophils Eosinophils Monocytes –1 20 25 23 24 × > 1. n = n = n = n = x 19 23 20 23 Prevalence established by detection of circulating Prevalence Three doves were sampled in 2003, one of which was positive for positive sampled in 2003, one of which was were Three doves Range if and one terrestrial species (Galápagos Dove) sampled in 2004, inhabiting a multispecies seabird colony on Isla Genovesa, Galápa sampled in 2004, inhabiting a multispecies seabird colony on Isla Genovesa, and one terrestrial species (Galápagos Dove) a b c Abbreviations: PCV = packed erythrocyte volume, WBC = white blood cell count, NA = not available. WBC = white blood cell count, NA Abbreviations: PCV = packed erythrocyte volume, 54 ± 5 4.8 ± 2.7 n = 54.0 ± 11.1 36.2 ± 10.9 0.5 ± 0.8 4.4 ± 1.8 4.9 ± 4.2 3 of 19 1.00 0.89 51 ± 3 9.4 ± 3.5 n = 46.7 ± 14.3 34.4 ± 14.2 0.5 ± 0.7 15.4 ± 7.9 3.8 ± 2.2 0 of 25 0.00 0 (%) µL (%) T 1. Hematological parameters and prevalence, intensity and aggregation level (var/mean ratio) of (var/mean intensity and aggregation level 1. Hematological parameters and prevalence, T PCV WBC 50 ± 7 10.3 ± 4.7 n = 36.1 ± 16.7 54.8 ± 17.5 0.2 ± 0.4 5.2 ± 3.6 3.7 ± 2.6 2 of 23 1.00 0.95 NA NA n NA 18 ± 5.7 69.06 ± 10.17 0.06 ± 0.24 8.4 ± 8.1 4.41 ± 2.28 11 of 26 29.36 225.76 55 ± 8 7.5 ± 2.7 n = 39.0 ± 8.5 40.0 ± 12.0 0.6 ± 0.9 17.9 ± 2.7 2.5 ± 1.6 7 of 24 1.29 1.12 GALÁPAGOS SEABIRD HEALTH SURVEY 91
F l. 1. Photomicrographs of hemoparasites in Galápagos birds. (A) Erythrocytes from a thin blood smear from Galápagos Dove. Arrow indicates a Haemoproteus-like parasite. (B) Erythrocytes from a thin blood smear from Great Frigatebird. Arrows indicate Haemoproteus-like parasites.
0.036, n = 16). Low prevalence in the other two Plasma-chemistry values showed no sex- infected seabird species precluded using this related diff erences, with the exception of test to compare the heterophil-to-lymphocyte plasma phosphorus (Table 3). A trend seen concentration ratios between infected and unin- across species was that females had higher fected birds. phosphorus levels (U = 1,135, P = 0.04, n = 81), 92 ORNITHOLOGICAL MONOGRAPHS NO. 60
) and slightly higher total plasma calcium levels –1 (U = 958.5, P = 0.01, n = 81). Within species, phosphorus values were higher in female than in male Nazca (U = 119.5, P = 0.0002, n = 23), ) (g dL ) (g
–1 Red-footed Boobies (U = 30, P = 0.03, n = 20), and Swallow-tailed Gulls (U = 22, P = 0.9, n = 14), but 94 ± 0.1 2.6 ± 0.4 not in Great Frigatebirds (U = 71.5, P = 0.9, n =
) (g dL ) (g 24). This diff erence was considered signifi cant 0.8 1.57 ± 0.4 1.8 ± 1.3 –1 0.3 1.17 ± 0.1 2.0 ± 0.9
± 0.4 1.22 ± 0.1 2.4 ± 0.6 in Nazca Boobies. ) (g dL ) (g
novesa, Galápagos Islands. novesa, D –1
Cl- protein Albumin Globulin Albumin Cl- protein We observed Haemoproteus parasites in periph- eral blood smears from three of four species of ) (mmol L
–1 Genovesa seabirds, as well as in the sympatric
+ and endemic Galapagos Dove. Hemoparasites K in the Haemoproteus genus have tradition- ally been considered incidental and relatively ) (mmol L ) (mmol –1 nonpathogenic parasites of birds and reptiles, +
) though eff ects on host fi tness components have been demonstrated (Merino et al. 2000, Marzal )
) et al. 2005), and pathogenicity has been shown ) (mmol L ) (mmol ) –1 for certain hosts of certain hemoparasite species (Earlé et al. 1993, Garvin et al. 2003). However, Phos Na
Sula sula molecular phylogenetic studies of malarial par- ) (mg dL ) (mg Fregata minor Creagrus furcatus
–1 asites has revealed considerable convergence Sula granti
++ in the morphological and life-history traits used traditionally to classify lineages (Perkins and Schall 2002). Furthermore, Haemoproteus ) (mg dL ) (mg
–1 parasites may not be monophyletic (Perkins and
Nazca Booby ( Schall 2002). Galapagos Doves exhibited the Red Footed Booby ( highest hemoparasite prevalence and parasit- Great Frigatebird ( emias, though most individuals were sampled Swallow-Tailed Gull ( Swallow-Tailed ) (mg dL ) (mg
–1 one year aV er the seabirds were. Thus, these dif- ferences within and among host species may be a ributable to diff erences in exposure to vectors (Sol et al. 2000), host physiology (constrained by phylogeny or life history) or genetics, parasite ) (mg dL ) (mg
–1 factors (strain type or within-host evolutionary dynamics), environmental conditions, or a com- bination of these and other factors (Goater and Holmes 1997).
) (U L ) (U The pathogenicity of these parasites in the sea- –1 birds and doves sampled, or the eff ects on host fi tness or reproductive success, are unknown. However, within Great Frigatebirds, birds
) (U L ) (U infected with Haemoproteus parasites exhibited –1 signifi cantly higher heterophil-to-lymphocyte concentration ratios than uninfected birds. In chickens, this ratio increased when birds were ) (mg dL ) (mg
n exposed to social stress or corticosterone in feed, and it is thus considered to be a reliable 24 12.1 ± 7.2 871.8 ± 271.1 14 310.3 ± 141.7 0.47 ± 0.3 252.0 ± 34.6 9.5 ± 0.64 7.5 ± 5.9 5.6 ± 2.6 263.3 ± 323.1 154.5 ± 3.6 361.6 ± 172.2 3.0 ± 1.2 1.2 ± 1.6 117.9 ± 3.2 3.76 280.6 ± 31.8 11.0 ± 2.9 4.6 ± 4.9 155.0 ± 9.2 3.0 ± 0.7 122.2 ± 7.5 4.13 ± 21 10.9 ± 8.2 940.1 ± 371.4 465.8 ± 181.1 0.6 ± 0.2 180.5 ± 64.0 9.3 ± 0.7 10.8 ± 4.6 151.4 ± 3.7 6.6 ± 2.1 116.0 ± 4.7 3.56 ± 24 7.7 ± 556 ± 421 248.1 ± 95.1 0.6 ± .5 212.1 ± 45.7 9.1 ± 0.66 4.7 ± 1.5 145.4 ± 8.2 3.0 ± 1.6 114.6 ± 4.5 3.58 ± 0.5 0. size ( size Total Total Total Sample acid Uric CK AST bilirubin Glucose Ca T 2. Plasma biochemistry values of four seabird species sampled in 2003 inhabiting a multispecies colony on Isla Ge 2. Plasma biochemistry values T indication of environmental stress (Gross and GALÁPAGOS SEABIRD HEALTH SURVEY 93
F l. 2. Boxplot showing mean (dotted line within box), median (solid line within box), 25th and 75th per- centiles (lower and upper box limits), and 5th and 95th percentiles (whiskers) for the ratio of heterophil to lymphocyte concentration from Great Frigatebirds on Isla Genovesa, Galápagos (standard differentials from thin smears were transformed into concentrations by multiplying the total white-blood-cell values (WBC × 1,000 µL–1) with the differential value, divided by 100). Mean ratios of heterophils to lymphocytes were signifi- cantly higher in birds positive for Haemoproteus infection than in birds negative for Haemoproteus infection (U = 9, two-tailed P = 0.036, n = 16).
T 3. Plasma phosphorus (mg dL–1) values in infected Great Frigatebirds is notable, and the reported by sex of four seabird species sampled in direction of causality should be investigated. 2003 inhabiting a multispecies seabird colony on Work and Rameyer (1996) did not fi nd signifi - Isla Genovesa, Galápagos Islands. cant diff erences in blood chemistries between Male Female P infected and uninfected Great Frigatebirds in Great Frigatebird (Fregata minor) Hawaii, though there were no signifi cant dif- 4.9 ± 1.69 4.5 ± 1.21 0.9 ferences in Haemoproteus infection prevalences n = 14 n = 10 between Hawaii and Galápagos, and parasit- Red Footed Booby (Sula sula) emias were relatively low in both studies. 8.6 ± 4.12 13.3 ± 3.93 0.03 In general, hemoparasites have been con- sidered rare in wild populations of seabirds n = 10 n = 10 Nazca Booby (S. granti) (Greiner et al. 1975, Peirce 1981, Bishop and 4.6 ± 0.66 6.8 ± 3.56 0.0002 Benne 1992, Benne et al. 1994, Jovani et al. n = 13 n = 10 2001). More recent reports, however, show that Swallow-Tailed Gull (Creagrus furcatus) prevalences of hemoparasites can be quite high 1.7 ± 1.10 8.4 ± 5.40 0.9 in some wild populations of seabirds (e.g. gulls: n = 8 n = 6 Esparza et al. 2004, Ruiz et al. 1995, Martínez- Abraín et al. 2002; frigatebirds: Work and Siegel 1983). Alternatively, this fi nding could Rameyer 1996, 1997), whereas they are still rare simply be a consequence of a direct immune in other groups (e.g. penguins: Jones and Shellam response to malarial pathogens. Although only 1999a, b). A previous study of another Galápagos correlational, our fi nding of signifi cantly higher seabird, the Waved Albatross, on the island of heterophil-to-lymphocyte concentration ratios Española, showed no evidence of hemoparasites 94 ORNITHOLOGICAL MONOGRAPHS NO. 60
(Padilla et al. 2003), though Haemoproteus-like between individuals during these long-distance organisms are extremely common in Galapagos movements. Therefore, placing Haemoproteus Doves on the same island (Padilla et al. 2004). lineages from Galápagos and Hawaiian popula- Relatively long embryonic development peri- tions of Great Frigatebirds and the Haemoproteus ods of seabirds (Ricklefs 1992) and the relative lineages from the two other Genovesa seabirds paucity of competent vectors in marine envi- in a broader phylogenetic context is warranted. ronments (Jovani et al. 2001) were proposed as When compared with hematologic param- hypotheses explaining the general absence of eters published for other adult free-ranging blood parasites in seabirds. Interestingly, Great Red-footed Boobies and Great Frigatebirds, Frigatebirds have an extremely long, 57-day the ranges of total WBC counts are comparable incubation period and provide parental care for (Work 1996, 1999). We observed slightly higher one year aV er hatching (Dearborn et al. 2001); yet PCV values and slightly lower total WBC counts Haemoproteus parasites have been reported from in Great Frigatebirds, but our values were com- at least three populations of Great Frigatebirds, parable to previously published biological though infection intensities were relatively low ranges for that species in the wild (Work 1996). in Hawaii and Galápagos (Hawaiian Islands: Female gulls and the two sulid species tested Work and Rameyer 1996; Galápagos Islands: had higher phosphorus and calcium levels than present study). males, but this was only signifi cant for phos- Haemoproteus parasites can be vectored by phorus. Work (1999) observed higher phospho- hippoboscid fl ies and ceratopogonid midges rus values in breeding female Brown Boobies (S. (Atkinson 1991). Although no ceratopogonids leucogaster) than in males of that species, which were reported from Hawaii, several spe- is consistent with our fi ndings, though we did cies occur within the Galápagos Islands (B. J. not diff erentiate breeding from nonbreeding Sinclair pers. comm.). Given the absence of females at time of sampling. Reproductive ceratopogonids in Hawaii, Work and Rameyer status, dietary preferences, or diff erent activ- (1996) speculated that the Haemoproteus present ity levels can be speculated as explanations for within Great Frigatebirds was likely vectored these diff erences. This relationship was absent by Olfersia hippoboscid species that associated in Great Frigatebirds in both studies and has not with Pelicaniform birds and that they observed been observed in other Pelicaniformes. In gen- on Great Frigatebirds. Olfersia species are also eral, plasma-chemistry values were comparable present in the Galápagos, and O. aenescens, to those published in the literature for other which is associated with Pelicaniformes, was species of the same taxa. collected in light traps on Genovesa during the The absence of C. psi aci antigen in all the 2004 sampling. Galapagos Doves also harbor a birds tested is notable, and the absence of C. species of hippoboscid (Microlynchia galapagoen- psi aci antibodies by elementary body aggluti- sis), and hippoboscids are oV en restricted to a nation (EBA) suggests that none of these birds few host families or orders (Maa 1963). Thus, had active clinical infections. In a previous study presently it is impossible to implicate either on Galapagos Doves, C. psi aci was present only hippoboscids or ceratopogonids as vectors in doves from Isla Española (Padilla et al. 2004), of Haemoproteus among the four bird species which, like Genovesa, contains large congrega- infected on Genovesa. Further characterization tions of colonial seabirds. Charadriiforms (gulls and diff erentiation of the Galápagos seabird and terns) have been reported as commonly hemoparasites through molecular techniques infecting free-living birds (Brand 1989), but few (e.g. Bensch et al. 2000, Schrenzel et al. 2003) and studies have documented C. psi aci infections in long-term studies will help illuminate the biol- wild seabirds (Franson and Pearson 1995). ogy of these hemoparasites and their ecological The present study presents baseline health implications at the population level and may parameters for a free-ranging colony of several reveal whether these birds share hemoparasite species of seabirds in the Galápagos Islands. The lineages and vectors. Great Frigatebirds exhibit most notable fi nding is the presence of hemo- high philopatry to nesting sites, but travel thou- parasites in three of the seabird species surveyed sands of kilometers from their nesting islands and in a sympatric terrestrial endemic bird, along (Dearborn et al. 2003), creating opportunities with associated signs of physiological stress for transmission of vectors and Haemoproteus in Haemoproteus-infected Great Frigatebirds. GALÁPAGOS SEABIRD HEALTH SURVEY 95
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