TEMPORAL DYNAMICS OF FARMLAND AVIAN DIVERSITY: EVALUATING BIRD
ASSEMBLAGES IN CROP FIELDS BEFORE AND AFTER HARVEST IN CENTRAL NIGERIA
Abstract
Though agriculture has been linked to the decline in bird populations
due to the associated changes in vegetation structure and composition,
its potential to sustain birds has been explored over time. A
sustainable agricultural landscape should be one that has the capacity
to support bird species all year. To this end, we investigated the
factors influencing pre- and post-harvest farm conditions on bird
abundance, richness, and feeding guilds in three different crop fields
in Jos-East and North, central Nigeria. We used line transects to survey
birds and vegetation variables from 30 fields each of legumes, maize,
and mixed (maize and soya bean) during the pre- and post-harvest periods
in central Nigeria. We first compared the variation in bird species
richness, abundance, and feeding guild abundance across the three field
types over the two periods. We then modeled the effects of field
conditions and vegetation parameters on feeding guild abundance, species
abundance, and species richness as response variables. Our results
revealed significant variations in bird species richness, abundance, and
feeding guild abundance across field types. The omnivorous guild was
significantly higher pre-harvest than post-harvest whereas insectivorous
and granivorous were significantly higher in-field than at the edge.
Bird species richness, abundance, and feeding guild abundance were
significantly higher pre-harvest than post-harvest and in-field than at
the edge. In addition, in-field tree density had a significant positive
influence on bird abundance and species richness as well as feeding
guild abundance. This study shows that pre- and post-harvest conditions
of crop fields can moderate the number and richness of birds on
farmlands while the retention of trees on farmlands contributes to
higher bird assemblages.