Colius

Abstract: of colies, their frequent sunbathing, and ocproduced fell through the platform and sank beneath a 2-cm layer of mineral oil in the bottom of the casional instances of hypothermia (often in chamber, thus minimizing fecal contributions to the birds with wet plumage), have led to the sugmeasurement of evaporative water loss. The respiromgestion that they may undergo periods of eter chamber was equipped with ports for the introtorpor (McAtee 1947; Bartholomew et al. duction and removal of air, a thermocouple, and an electic humidity sensor. Dried air was passed 1957; Cowles 1959). Their thermoregulatory through the respirometer chamber at 700 cc/min capacity, however, has never systematically at ambient temperatures of 5-40°C; at 42°C the rate been studied, and despite their abundance and was increased to 1590 cc/min. Evaporative water the many unusual features of their structure loss was determined from the change in weight of

Abstract: Summary. Histological and moult data are given for series of three species collected at fortnightly intervals over one year at Amani, an evergreen locality in Africa at 5 °. The species are Colius (Mousebird, a small non-passerine) and two Pycnonotidae (Bulbuls), one, Phyllastrephus, living inside the forest, and the other, Pycnonotus, outside. Moult is regular, concentrated and seasonal in both Pycnonotidae; “early” stage and even “mid” stage of wing-moult are found in both these birds concurrently with enlarged testes and free sperms. These conditions do not seem to have been reported before for small passerines. In Colius moult is irregular and proceeds indefinitely irrespective of testis-state: continuance of wing-moult through the breeding season seems hitherto to have been recognized only in large birds dependent on full wing-efficiency for their livelihood. In all three species testes are biggest from September to March, when they regress sharply and do not approach the maximum again till August. These results accord with field observations on nests. In the resting period, which covers the “long rains” and the subsequent cool season, the internal state of the testes is like that of temperate-zone birds in winter. Recrudescence takes place when there has been practically no increase in temperature above the annual minimum and day-length is increasing at less than 20 seconds a day. Lines of further research are suggested. The annual increase in testis size is about 30 times in the Pycnonotidae and 8 in the Colius. Other data for tropical and temperate-zone species are quoted, from which it appears that the latter tend to have a much greater increase in testis size (up to 2,000 times). In Amani birds spermatogenesis commonly takes place in testes that have not attained full size. In the ovaries atretic follicles, rare in temperate-zone birds, are abundant and may be an adaptation to high nest-mortality.

Abstract: . The preferences that bird species exhibit for different sugar types may play a role in pollinator-mediated selection on plant nectar composition. How bird sugar-type preferences are affected by concentration is a fundamental question for research that aims to use those preferences to explain plant nectar composition. Such research has been done for several specialist avian nectarivores, and for a few passerine occasional nectarivores, but not, apparently, for any nonpasserine occasional nectarivore. We examined the effect of concentration of sugar solutions on sugar-type preferences of the Speckled Mousebird (Colius striatus), a common African nonpasserine that occasionally feeds on floral nectar. Surprisingly, the species exhibited a concentration-dependent switch in sugar preference, from hexose sugars at low concentration to sucrose at high concentrations, that was remarkably similar to that shown by specialist avian nectarivores and that contrasts with results reported for passerine occasion...

Abstract: Summary Earle, R. A. 1981. Factors governing avian breeding in Acacia savanna, Pietermaritzburg, Part 2: Intrinsic factors. Ostrich 52:74-83. The most important factor governing avian breeding in Acacia savanna is the body condition (protein reserve) of the bird. Breeding can take place only if the female has a large enough protein reserve to form eggs. The protein reserve is dependent on an adequate food supply which is once again dependent on climatic factors. Both the protein reserve and body weight of several species were found to be at their lowest towards the end of the breeding season. Moult and breeding were found to be largely separated in time. In most species examined testis activity was at its lowest between April and June and highest from September to January. Colius striatus showed a less seasonal pattern of testis activity while Nectarinia talatala showed very early testis activity and had fully active testes in May.