Sperm competition is the competition between sperm from two or more males to fertilize the egges of a single female during one reproductive cycle. Recently many ornithologists have focused on this theme, and are studying many bird species by using biochemical methods (e. g. DNA fingerprinting). I review almost all of the important literature on avian sperm competition of the last decade, and discuss the evolution of social behaviour of both sexes through sperm competition. Sperm competition is an essential process of intrasexual selection which influences not only the characteristics of reproductive organ and mating behaviour, but also the mating system, social organization and life history strategy of birds. It is a co-evolutionary process between both sexes.
The breeding ecology of the Coot Fulica atra was studied on Lake Teganuma, Chiba, central Japan, from April to October 1990. Nests were built in 2-7 days, and used for copulation and egg laying. The egg laying period ranged from early April to mid-July, peaking in May. One egg was laid per day and clutch size varied from 3-8 eggs, with an average of 5.2. Eggs weighed between 30 and 40g, averaging 34.9g. The mean size of 120 eggs from 23 nests was 52.0×35.5mm. Most nests (86%) were placed in Typha angustata, and the other nests (14%) in Zizania latifolia. Both males and females incubated eggs. The interval of incubation was 51 minutes on average. The incubation period ranged between 21 and 25 days. The second nest was constructed once the eggs had hatched. Of a total of 126 eggs laid in this study area, 32% hatched, with only 12% of the eggs remaining after two weeks.
Quinalphos, an organophosphorous pesticide, was administered orally to sexually mature male Whitethroated Munias at different doses (5μg-, 10μg- and 20μg/100g body wt./day) for 1-, 5-, or 10 day(s). Testicular responsiveness to the treatment in each group was analyzed by comparing the testes with control (vehicle treated) birds. A significant decrease in the paired testicular weight, and in the number of seminiferous tubules containing healthy germ cells was noted following the treatment of each dose of pesticide for 5- and 10 days. A number of degenerative changes in the testicular germ cells were found in different groups of quinalphos ingested birds, but no degenerative feature could be ascribed as a marker to the level of exposure. The activity of acetylcholinesterase (AChE) in the testes of quinalphos treated munias was inhibited in a dose- and duration-dependent manner. A significant negative correlation was found between testicular AChE activity and percentage of degenerated germ cell containing tubules. However, no conspicuous difference was noted in the Leydig cells of the testes in the control and treated bird groups. The results of the present study indicate that ingestion of quinalphos is injurious to the gametogenic functions of the testis in a wild passerine bird and that the antigonadal action of the pesticide may be pharmacological in origin.
Bird communities were investigated using a linetransect census method at four areas along the middle reaches of the Tokachi River, eastern Hokkaido. Survey were conducted from mid-May to early July, 1980-82. Six 50m by 2km transects were established at four areas. Twenty two to 41 bird species were recorded among transects, peaking in mixed forest and glassland habitat. Common bird species for which their relative abundance was 2% or more were Gallinago hardwickii, Alauda arvensis, Saxicola torquata, Turdus chrysolaus, Locustella fasciolata, Acrocephalus bistrigiceps, Emberiza spodocephala and Sturnus cineraceus. These species prefer mainly open habitats. Waterfowl, waders, Ripa riariparia, Motacilla alba and M. grandis were common in transects bordering the river, or with an open area without vegetation. Shannon-Weaver's species diversity indices (H'), based on the number of birds counted in May and June, ranged from 3.24 to 3.84. Whittaker's similarity indices between transects were high among transects with similar habitat characteristics. Although riverine and adjacent areas have been modified by various riparian works, they continue to provide shrub-grassland birds with an important habitat.