Breeding performance of Yellow – Eared Bulbuls in Riverstan of Dumbara Massif

Abstract

The breeding behavior of the endemic Yellow - Eared Bulbul ( Pycnonotus penicillatus) was studied from December 2011 to May 2012 in Northern flank of the Knuckles mountain range. No systematic investigation of the breeding ecology of Yellow - Eared Bulbul has been done before. Nests were located during one field season from the arrival (March) to the dispersal of the birds (May) and collected data on various breeding parameters, availability of fruits and weather conditions. While noted nests observing other activities were also counted. Behavioral observations of the birds were made from 6.00 hrs to 18.00 hrs in selected habitats. Scan sampling and focal animal sampling techniques were used to gather data. The nests were checked every day at two three day intervals during the incubation and hatching periods and at weekly intervals from the time chicks hatched, till they leave the nest. All nests were found in mid-elevation evergreen forests ranging from 5m to 8m elevation. Breeding occurred in the dry season from mid February to the end of May which coincides with high fruit availability. One of the most preferred fruit tree species of Yellow – eared Bulbul was Ilex knuckelensis. The fruit ripening of this plant is the time when hatchlings emerge. The peak egg-laying was in March and April. Both sexes participated in nest building and construction took 5 – 8 days to complete (mean = 6.58 ±1.43 days, n = 8). Majority of the nests (>48%; n = 10) were built on Eleocarpus glandulifer plants and Bambusa multiplex and the mean nest height was 4.62± 1.26 m. They used nearby plant species as collecting places of nest construction materials. Mostly the leaves of Bambusa multiplex, Elettaria cardamomum and mosses. Nests were open cups placed 3-7m from the ground in plants of 4-10 m tall. The clutch size of Yellow – Eared Bulbuls ranged from one to two with 87.5% of nests containing two eggs (mean clutch size: 1.08±0.39 eggs, n=15) .Average length of the incubation period was 12.57±0.48 days (range:11-13 days , n= 8). Nestling period ranged from 12 to 13 days (mean: 12.65±0.54 days, n= 6). Average breeding season lasted for thirty days.