The ecology of Meyer's parrot (Poicephalus meyeri) in the Okavango Delta, Botswana.

Abstract

Meyer’s Parrot Poicephalus meyeri is the smallest of the nine Poicephalus parrots, forming the P. meyeri superspecies complex with five congeners. Their distributional range far exceeds any other African parrot, extending throughout subtropical Africa. Meyer’s Parrots had previously not been studied in the wild, and therefore, gathering high-quality empirical data on their behavioural ecology became a research and conservation priority. The primary aim of the study was to correlate environmental (e.g. rainfall, habitat availability, resource characteristics, food resource abundance and temperature) and social (e.g. inter- and intra-specific competition, predation, and human disturbance) variables with aspects of their ecology (e.g. flight activity, food item preferences, breeding activity, and group dynamics) to evaluate the degree of specialization in resource use (e.g. trophic, nesting and habitat niche metrics). African deforestation rates are the highest in the world, resulting in twelve out of the eighteen Meyer’s Parrot range states undergoing drastic loss of forest cover over the last 25 years. Most commentary on the population status of Meyer’s Parrots and other Poicephalus parrots pre-dates this period of rapid deforestation In addition, over 75 000 wild-caught Meyer’s Parrots and almost 1 million wild-caught Poicephalus parrots have been recorded in international trade since 1975. Empirical data from this study was used to identify ecological weaknesses (e.g. niche specialization or low breeding turnover) for evaluation within the context of deforestation in the African subtropics. Baseline data on the breeding biology and nest cavity requirements of Meyer’s Parrots was also necessary to assess the viability of applying the conservative sustained-harvest model to African parrots. A unifying goal of this study was to advance our knowledge of the ecology of African parrots and other Psittaciformes by assessing the validity of current hypotheses put forward in the literature. The Meyer’s Parrot Project was initiated in January 2004 on Vundumtiki Island in the north-eastern part of the Okavango Delta, Botswana. Due to high flood waters between March and July 2004, road transects were postponed till August 2004. Transects were conducted at Vundumtiki from August 2004 to July 2005 and February 2007 to August 2007, and at Mombo from August 2005 to January 2006. During 480 road transects over 24 months, food item preferences closely tracked fruiting and flowering phenology, resulting in significant positive correlations between Levins’ niche breadth, rainfall and food resource availability. Meyer’s Parrot can, therefore, be considered opportunistic generalists predispersal seed predator that tracks resource availability across a wide suite of potential food items, including 71 different food items from 37 tree species in 16 families. Meyer’s Parrots were, however, found to be habitat specialists preferring established galleries of riverine forest and associated Acacia-Combretum marginal woodland. These strong habitat associations facilitate their wide distribution throughout the Kavango Basin, Linyanti Swamps, down the Zambezi valley, up along the Rift Valley system in associations with the great lakes, through the Upper Nile and the Sudd, and west as far as Lake Chad through the Sahel. Seventy-five nest cavities were measured during this study, including 28 nest cavities utilized by Meyer’s Parrots within the 430ha sample area at Vundumtiki. Over 1700 hours of intensive nest observations at six nest cavities was undertaken. Meyer’s Parrots formed socially monogamous pair-bonds maintained over at least four breeding seasons. Breeding pairs established breeding territories up to an estimated 160ha within which there were 1–6 nest cavities. Eggs hatched asynchronously, yet nestlings fledged synchronously with similar body size and condition. There was evidence to support the incidence of extra-pair copulations, however, mitochondrial DNA sequence data are required to confirm the incidence of extra-pair fertilizations. Meyer’s Parrots had no preferences in regard to nest tree species beyond the incidence of suitable nest cavities, which are selected and further excavated to accommodate their non-random nest cavity preferences. There was a significant non-nesting Meyer’s Parrot population during the breeding season, likely due to this longlived cavity-nester delaying nesting until a suitable breeding territory becomes available. Meyer’s Parrots utilize communal roosts during summer and disperse from them according to the Foraging Dispersal Hypothesis. Due to the requirement to roost during the middle of the day to avoid heat stress, Meyer’s Parrots have bimodal flight and feeding activity patterns. The highest probability of locating Meyer’s Parrots is between 08h30 and 11h00 during summer when both adults are feeding on the seeds of fleshy-fruits in riverine forest communities. Due to the paucity of data on the current distribution and population status of Meyer’s Parrots and other African parrots, a continent-wide survey of all African parrots represents a conservation priority. Current deforestation rates in several Meyer’s Parrot range, their specialist habitat associations, and lack of evidence to support adaptability to a changing landscape mosaic necessitate the re-classification of Meyer’s Parrots as data deficient or nearthreatened. Based on low breeding population due to limited breeding opportunities, the CITES Appendix II wild-caught bird trade should also be halted until the sustainability of this trade has been evaluated and the relevant information made available.