Most of the birds respond to angiotensin II (ANG II) (ip, 1-10μg/100g) by drinking. The receptive sites for ANG II are the preoptic area and the subfornical organ in the brain. However, species originating in arid areas and carnivorous birds, which drink little water in nature, are relatively insensitive to ANG II. It seems that ANG II has become adaptively involved in the physiological mechanisms inducing thirst during the evolutionary process. Among various other neuropeptides some have stimulatory and others inhibitory or no effects on water intake. Receptive sites for the active neuropeptides are located centrally, peripherally or in the kidney. However, it is not known whether the action is physiological in nature or not.
Annual testicular events in free-living Roseringed Parakeets were studied in relation to climatological variables over three consecutive years. Functional status of the testis was determined from paired testicular weight, seminiferous tubular diameter, spermatogenetic index, Leydig cell nuclear diameter and quantity of total testicular cholesterol. Based on these analysis the annual testicular cycle was divided into five different phases, namely regenerative or preparatory phase (May-August; resting spermatogonia present in the regressed tubules); progressive phase (Sept.-Dec.; recrudescence of gametogenesis occurs); prebreeding phase (Jan.-Feb.; spermiogenesis starts but at slow rate); breeding phase (March; active spermatogenesis occurs); and regressive phase (April-May; degenerative changes occur in the germ cells). A new generation of Leydig cells appeared during the preparatory phase and matured during the progressive phase. Signs of Leydig cell hyperactivity were detectable till the end of the breeding phase. However, statistical analysis failed to identify any environmental component that may have induced seasonal testicular maturation in free-living Roseringed parakeets.
An indirect method for censusing shorebirds is described which uses a marker species of known abundance to gauge the abundance of other species on tidal flats at low tide. Shorebirds were censused using the indirect method at Yatsu tidal flat, Tokyo Bay, and the counts compared with estimates derived from total scan counts. The generally close agreement between the two methods suggests that the indirect method may be a useful alternative method for censusing shorebirds, particularly when the intertidal areas are large and when few people are available to conduct the censuses.
Seasonal changes in the number of eight resident species were analyzed using census data for a single year in a local avian community. Censuses were divided into four groups according to the results from cluster analysis based on the number of individuals from each family. These groups were distributed according to season, and discriminated by mean daily temperature and mean wind velocity among other meteorological variables. The number of individuals of Pycnonotidae, Turdidae, Sylviidae, Muscicapidae, Zosteropidae, Emberizidae and Fringillidae differed significantly among the four groups. Turdidae, Emberizidae and Fringillidae consisted mainly of winter visitors and discriminated the four groups in 63.9% of cases. The two meteorological variables, the number of 4 migrant families and the number of other residents were used in analyses of factors affecting the number of each resident by dividing the data into two seasons. Selected variables that explained the number of eight residents differed between the two seasons, suggesting that interactions effecting habitat selection among resident species changed seasonally.