Reproductive Advantages for Common Loons Using Rafts

Abstract: Artificial nesting islands, or rafts, are often deployed in common loon (Gavia immer) breeding territories to decrease negative impacts of mammalian predation and water-level fluctuations on nesting success. The management value of rafts has been demonstrated in other studies; however, no published studies have quantified the use or associated reproductive benefits of rafts on lakes exhibiting water-level fluctuations. These lakes constitute a major portion of loon nesting habitat in New England and the Midwest. We used long-term data sets from loon survey and raft management efforts on lakes with stable (SWL) and fluctuating water levels (FWL) in New Hampshire and Maine, USA, to compare raft-use patterns on both types of lakes. We then modeled the influence of percentage of nesting attempts on rafts, lake fluctuation type, and human development index on nesting success as a function of the number of nesting attempts. Loons used 76% of all rafts for nesting, and initial use patterns were similar between SWL and FWL lakes. Half (51%) of rafts used for nesting were first used during the initial year of deployment and 90% of those used were used by the third year. Based on our model, we would expect to see an 8.6% increase in nesting success associated with each successive categorical increase in raft use (0–33%, 33–60%, 60–100%). Nesting success varied with lake fluctuation type, increasing by 21.4% from FWL to SWL types. Our model estimated a 12.8% decrease in nesting success associated with an increasing human development index. Naturally nesting loons on FWL lakes are likely to display mean nesting success levels lower than those needed to sustain populations. We suggest that natural nesting habitat on lakes with fluctuating water levels during the loon nesting season may constitute an ecological trap warranting consideration of raft management. Findings in this study are germane for managing breeding loon populations, particularly those on reservoirs requiring permits from the Federal Energy Regulatory Commission.     

Fine-Structural Aspects of Macrogametogenesis in Eimeria magna*†

SYNOPSIS. Macrogamonts in tissues from rabbits killed 5 1/2 days after inoculation with Eimeria magna oocysts were studied with the electron microscope. In young macrogamonts, parts of cytoplasm, sometimes including micronemes, were pinched off into the parasitophorous vacuole. In all stages of development, small segments of the inner membrane complex were present beneath the limiting membrane. Micropores also were seen in all stages, and some apparently functional ones were present in mature macrogametes. Wall-forming bodies of Type I and Type II were observed in relatively early stages. The former were less numerous than the latter, which had a more compact appearance than in other species. Usually, several Golgi complexes were present and several Golgi adjuncts occurred in the vicinity of the nucleus in all stages of development. Microgametes were observed in the cytoplasm of host cells harboring immature macrogametes.     

Hematozoa from Mammals of South Vietnam*

SYNOPSIS. Blood smears from 519 mammals of South Vietnam were examined for hematozoa. Trypanosomes were found in Rattus norvegicus, R. exulans, R. nitidus, and Rattus sp. Hepatocystis vassali occurred in squirrels Callosciurus flavimanus; erythrocytic stages and liver merocysts were seen. Fruit bats Cynopterus brachyotis and one insectivorous bat Hipposideros larvatus, harbored closely related but as yet unidentified hemosporidia. Piroplasms were found only in carnivores: ferret-badgers Melogale personata, palm civets Paradoxurus hermaphroditus, and mongooses Herpestes javanicus.