Mary C. Garvin

PATHOGENICITY OF HAEMOPROTEUS DANILEWSKYI, KRUSE, 1890, IN BLUE JAYS (CYANOCITTA CRISTATA)

Although the impact of blood parasite infections on passerine birds is potentially great, little is known of their pathologic effects. We studied Haemoproteus danilewskyi in experimentally infected captive and naturally infected free-ranging blue jays (Cyanocitta cristata) to determine patterns of infection and examine the pathologic effects of the parasite on the host. Physiologic changes, such as elevated numbers of lymphocytes, heterophils, basophils, eosinophils, and monocytes and decreased packed cell volume in the peripheral blood were associated with the erythrocytic phase of experimental infections of captive juvenile jays. Sublethal pathologic changes associated with the pre-erythrocytic phase of infections were observed in the liver, lung, and spleen. Schizonts were observed in the pulmonary capillaries of a 1 yr old jay necropsied 31 days post-inoculation, but not in 20 juvenile jays necropsied 57 days post-inoculation. In free-ranging naturally infected jays plasma protein concentration increased with density of natural infections.

BLOOD PARASITES IN BIRDS FROM MONTEVERDE, COSTA RICA

In a survey of avian blood parasites in Costa Rica, 51 (11%) of 479 birds sampled were infected by at least one species of hematozoan. Fourteen of the 60 species of birds in the survey were examined for the first time. Infections were most common in ramphastids and emberizids and infrequent in other taxa. Among resident species, infections were more commonly detected during the wet season when most birds breed than during the dry season when few birds breed. Infections caused by Haemoproteus sp. were most common, while Plasmodium sp., Leucocytozoon sp., Trypanosoma sp., and microfilarial infections were rare. The intensity of the 40 Haemoproteus infections in adult birds was low, with a mean ± SE of 12.5 ± 3.7 infected cells per 10,000. Haemoproteus infections did not undergo seasonal changes in intensity.

ECOLOGY OF CULICOIDES (DIPTERA: CERATOPOGONIDAE) IN SOUTHCENTRAL FLORIDA AND EXPERIMENTAL CULICOIDES VECTORS OF THE AVIAN HEMATOZOAN HAEMOPROTEUS DANILEWSKYI KRUSE

To determine the vectors of Haemoproteus danilewskyi in blue jays (Cyanocitta cristata) in southcentral Florida (USA), we conducted a 2 yr study from January 1993 to December 1995 of the presence and seasonal abundance of Culicoides spp. Of the 14 species of Culicoides captured in Centers for Disease Control light traps, 10 were ornithophilic. Of these, C. edeni, C. knowltoni, C. stellifer, C. beckae, and C. arboricola were most abundant, representing 46% of the total collection and 99% of the ornithophilic collection. The presence of C. stellifer in Bennett trap collections represents a new biting record for this species on passerine birds. We experimentally challenged the most abundant ornithophilic species to determine which were capable of supporting sporogonic development of H. danilewskyi. Culicoides edeni, C. knowltoni, and C. arboricola supported sporogonic development of H. danilewskyi.

Blood parasites of Nearctic-Neotropical migrant passerine birds during spring trans-Gulf migration: impact on host body condition.

To test the hypothesis that migrants infected with blood parasites arrive on the northern coast of the Gulf of Mexico in poorer condition than uninfected birds, we examined 1,705 migrant passerine birds representing 54 species of 11 families from 2 Gulf Coast sites for blood parasites. Three hundred and sixty (21.1%) were infected with 1 or more species of 4 genera of blood parasites. The prevalence of parasites was as follows: Haemoproteus spp. (11.7%), Plasmodium spp. (6.7%), Leucocytozoon spp. (1.3%), and Trypanosoma spp. (1.2%). Both prevalence and density of Haemoproteus spp. infection varied among species. We found no relationship of gender or age with the prevalence of Haemoproteus spp. infection or Plasmodium spp. infection, with the exception of the orchard oriole (Icterus spurius) for which older birds were more likely to be infected with Haemoproteus spp. than younger birds. We also found that scarlet tanagers and summer tanagers infected with species of Haemoproteus have lower fat scores than uninfected individuals and that rose-breasted grosbeaks and Baltimore orioles infected with Haemoproteus spp. have a smaller mean body mass than uninfected individuals. Blood parasites do seem to pose a physiological cost for Neotropical migrant passerines and may be important components of the ecology of these species.

AVIAN HEMATOZOA FROM WEST-CENTRAL BOLIVIA

A total of 641 birds representing 135 species of 25 families from Noel Kempff Mercado National Park in west-central Bolivia was examined for hematozoa; only 33 (5.1%) harbored blood parasites. Microfilariae were the most commonly encountered hematozoans, followed, in numerical sequence, by species of Haemoproteus and Plasmodium; Trypanosoma, Atoxoplasma, and Hepatozoon were seen infrequently. The survey included 13 new host-parasite records, and 58 species of birds were examined for blood parasites for the first time; 43 were parasite-free. The low prevalence of parasitism recorded in this survey is compared to other areas in the Neotropical region and to prevalence of blood parasites in the avifauna of other major land masses.

Epizootiology of Haemoproteus danilewskyi (Haemosporina: Haemoproteidae) in blue jays (Cyanocitta cristata) in southcentral Florida.

Prevalence and density of Haemoproteus danilewskyi was studied in a population of free-ranging blue jays (Cyanocitta cristata) in southcentral Florida (USA) from May 1992 to December 1995. Prevalence of infection was 27% for data combined over years, seasons, ages, and sexes. Prevalence did not vary between sexes or among years, but increased with age and varied with season, being highest in June–July and lowest in November–January. Parasite density did not vary between sexes or among seasons, but was higher in younger birds when controlling for season. To determine periods of natural transmission, seasonal patterns of infection were compared with previous month abundance of the biting fly vectors. Mean monthly prevalence of H. danilewskyi in older jays was positively correlated with previous month abundance of Culicoides edeni and C. arboricola, both capable of sporogonic development of H. danilewskyi.

HABITAT AND NESTING SUCCESS OF BLUE JAYS (CYANOCITTA CRISTATA): IMPORTANCE OF SCALE

Abstract Nesting success of birds often is influenced by habitat features surrounding nests. However, few studies have investigated habitat influences at multiple levels and spatial scales. We examined the relationship between Blue Jay (Cyanocitta cristata) nesting success and habitat at three levels (macrohabitat, microhabitat, and nest site) and at three different scales within the microhabitat level (3.1, 0.3, and 0.07 ha circular plots surrounding nests) in central Florida. We defined successful nests as those fledging at least one offspring. An eight-fold difference in probability of nesting success existed among seven distinct macrohabitats, with Mayfield success estimates ranging from 8 to 63%. However, no difference in number of fledglings per nest existed among macrohabitats when unsuccessful nests were excluded from the analysis. Macrohabitats in which nests were more often successful had more extensive slash pine (Pinus elliottii) forest. Logistic regression analyses indicated that slash pine canopy cover was significantly related to nesting success at all three microhabitat scales, although the tree species in which a nest was placed was unimportant to nesting success. Other microhabitat and nest-site features were unrelated to nesting success. Strong circumstantial evidence indicates predation was the major cause of nest failure, but relative abundance of one potential predator, the gray squirrel (Sciurus carolinensis), was not related to nesting success in macrohabitats or slash pine canopy cover within microhabitats. In this study, logistic regression models using habitat features measured at higher levels and larger scales had better predictive power, indicating that habitat may have influenced predation at scales larger than that of a typical nest patch.

Short-chain carboxylic acids from gray catbird (Dumetella carolinensis) uropygial secretions vary with testosterone levels and photoperiod

The uropygial gland of birds produces secretions that are important in maintaining the health and structural integrity of feathers. Non-volatile components of uropygial secretions are believed to serve a number of functions including waterproofing and conditioning the feathers. Volatile components have been characterized in fewer species, but are particularly interesting because of their potential importance in olfactory interactions within and across species. We used solid-phase microextraction headspace sampling with gas chromatography-mass spectrometry to detect and identify volatiles in uropygial secretions of gray catbirds (Dumetella carolinensis), a North American migratory bird. We consistently detected the following carboxylic acids: acetic, propanoic, 2-methylpropanoic, butanoic, and 3-methylbutanoic. We tested for the effect of lengthened photoperiod and/or exogenous testosterone on volatile signal strength and found a negative effect of lengthened photoperiod on the signal strength of propanoic, 2-methylpropanoic, and butanoic acids, suggesting a trade-off between their production and heightened night-time activity associated with lengthened photoperiod. Signal strength of propanoic and 2-methylpropanoic acids was lower in birds treated with exogenous testosterone than in birds treated with placebos. Sex did not affect signal strength of any of the volatile compounds.

Hematozoa from passeriform birds in Louisiana.

Blood smears were examined from 935 individuals of 19 migrant and resident bird species collected in Louisiana. Of these, 320 (34.2%) harbored hematozoa. The prevalences of parasites were as follows: Haemoproteus spp. 22.8%, Trypanosoma spp. 6.9%, unidentified microfilariae 5.0%, Plasmodium spp. 3.4%, and Leucocytozoon spp. 1.3%. These data are consistent with other reports from the region. Infections were observed in 33% of the individuals in the 13 migrant species sampled and 33% of the individuals in the 6 resident species.

Patterns of Haemoproteus beckeri parasitism in the gray catbird (Dumatella carolinensis) during the breeding season.

We determined the prevalence and intensity of blood parasites in breeding gray catbirds (Dumatella carolinensis) at Killbuck Wildlife Area in Wayne and Holmes Counties, Ohio (USA) from June through August 2000. Of 98 catbirds sampled, 40 (40.8%) had detectable infections of Haemoproteus beckeri. Overall prevalence of H. beckeri in this population is high relative to that reported in earlier blood parasite surveys of both breeding and migrant catbirds. Mean intensity of H. beckeri infection did not vary significantly between young and old birds or among sampling periods. We found no effect of age on prevalence or intensity of H. beckeri infection. Older birds were not more likely to be infected than younger birds, despite longer exposure to arthropod vectors. Prevalence varied significantly with season and was highest in June and lowest in August. This pattern also was observed in older birds sampled repeatedly. This seasonal variation may reflect both newly acquired infections and chronic infections relapsing in response to hormonal changes associated with breeding. Evidence of transmission was observed in the single hatching year bird that lacked detectable infection in early summer, but demonstrated a very high intensity infection in late summer. These observations provide supportive evidence that hematozoa infections are acquired on the breeding grounds during the first year of life and relapse during the breeding season in subsequent years.