Insects as important delicacy for birds: Expanding our knowledge of insect diet of birds in the tropics
Eighty percent of birds include insects in their diet. The species of insect more or less consumed often depends on the bird species and its stage in life. In terms of nutritional value, insect diet is adequate; because of its rich and easily digestible protein and fat, although the digestibility of various parts largely depends on their chitin content. This study was carried out in three sites; Kurra Falls Forest (9023’N, 8042’E), the Fobur District (9051’N, 9001’E) and the Jos Wildlife Park (09° 52', 08° 53') all located in Plateau State, Nigeria. In general all the study sites constitute similar vegetation structure and lanscape. All sites are typically savanna woodlands interspersed with gallery forests, patches of grasslands and rocky outcrops. Insect diet of the cattle egret Bubulcus ibisand insectivorous passerines were studied through faecal sample analysis. This involved collection of faecal droppings from roost sites and mist-netting. Birds were trapped using mist nets to obtain faecal droppings. Droppings were preserved and taken to the laboratory for examination of insect fragments. Line transect was used to survey birds while iinsects were sampled along the transects using sweep net and pitfall traps to correlate results of field and faecal sample data.
The Orders hymenoptera, orthoptera, coleopteran and diptera comprise the main insect food for cattle egret and insect eating passerines. These Orders also dominated insect samples collected from the field. The Families acrididae and formicidae constitute the major insect Families fed by the cattle egret and the insectivorous passerines. Examination of faecal droppings revealed that birds preyed primarily on the insect Orders hymenoptera (36%), coleoptera (23%), orthoptera (12%) and diptera (9%) which together represent 80% of the insectivorous passerines insect diet. Thirteen percent of the insect diet was made up of 9 insect Orders (lepidoptera, odonata, isoptera, homoptera, hemiptera, anoplura, mantodae, thysanoptera and tricoptera) and the remaining 7% were unidentified fragments. The study concludes that insects Orders identified from feacal droppings of birds correlates with insects sampled from the field. Choice of insects diet, therefore, showed that tropical birds may have a direct correlation between habitat resource availability and utilization which perhaps confirm that birds choose food opportunistically.