Birds Aggregated in One Particular Area Or Spot

SHORT FEATURE

M.C. BINDYA

Indian cuckoo

IRD enthusiasts often see a cluster Bof birds aggregated in one particular area or spot. These fl ocks may have members belonging to the same species or different species. Such fl ocks are common in most habitats including a town or village, or forests of any type – deciduous, littoral, mangrove, scrub vegetation, grassland or wet lands. However, not all birds show fl ocking behaviour. For example, the kingfi sher birds forage solitary. Some of the predatory birds like eagles rarely form fl ocks. So, why do most birds form Scarlet Minivet Male and Female A white throated kingfi sher fl ocks? Does the habit of forming fl ocks benefi t the birds in any way? Are there The greater racket-tailed drongo, any disadvantages in such associations? known for its aggressive behaviour Let’s examine the different probable and sometimes mobbing larger birds reasons why birds form fl ocks with especially when nesting (Popular members either belonging to some species Handbook of Indian Birds, 1949), mimics or of varied species. the sounds of scarlet minivet perfectly and perches on a branch in their vicinity. Increased vigilance and protection While the other birds will be picking up In the moist deciduous forests of and gleaning the insects off the leaves, Panchawati, a village in Middle the racket-tailed drongo stays still and Andaman, a fl ock comprising birds like alert. The chirping, ringing high pitched scarlet minivet (Pericrocotus fl ammeus, whistles of each bird species resonates both male and female), Asian fairy in the otherwise quiet forest. The drongo blue bird (Irena puella), brown shrike raises an alarm on seeing a predator like (Lanius cristatuslucionensis), black naped the Andaman serpent eagle or white oriole (Oriolus chinensis), black headed bellied sea eagle making the birds break confront a predator they quickly take off bulbul (Pycnonotus atriceps), oriental up in different directions. For this reason initiating the same response in other birds white eye (Zosterops palpebrosus) and the nests of many of these birds are close (Study in Ostriches, Bertram 1980). Thus greater racket-tailed drongo (Dicrurus to the breeding grounds of drongos. groups can detect predators sooner than paradiseus) is a common sight during day solitary individuals. time. Increasing Feeding Effi ciency Communal roosting also increases All of them have similar food Birds like sparrows or pigeons usually foraging effi ciency (Eiserer, Leonard A, habits with prey consisting of insects feed and roost in groups. When they are Bird Behaviour, Vol 5). While on fl ight such as beetles, cicadas, grasshoppers, feeding not all birds would pick on the the predator would fi nd it hard to hook dragonfl ies, moth or their larvae, food with their heads down, some of on to one bird from the fl ock (Split eff ect, caterpillars and so on. their heads would be raised up. If they Cousin et al. 2002) Science Reporter, MAY 2016 22 SHORT FEATURE

Black drongo

Social grouping (clockwise from top left): Cuckoo, Asian fairy bluee Clockwise from top right: Brown shrike, Chestnut headed bird, Asian koel, Black headed bulbul, Green imperial pigeon bee-eater, Blue tailed bee-eater ...we had heard that “birds of a feather fl ock together”. However, it is now apparent that Great racket-tailed drongo “birds of different feathers fl ock together as attempts to rob large well”. cuckoo shrike’s prey that traverse over grassy fi elds. They ones as crows or drongos. Cuckoos are hawk on grasshoppers and locusts that thus often chased by a fl ock of crows. fl ush from the grass that sways in wind. Black hooded oriole An interesting case of a black drongo Although they belong to different species raising alarm calls on spotting a cuckoo or variety they never intimidate one was seen in an open forest of Kerala. This Spotted owlet another. Different varieties of egrets also act of drongos prompted the crows to get along well when foraging on grass. ward off the unfavourable visitor. Reducing However, feeding in fl ocks is not Competition Warding Off Predators without detrimental effects. In the forest Yellow billed babbler Groups or undergrowths of Kerala yellow billed During the nesting season predators colonies may babblers (Turdoides affi nis), common like owls, eagles and hawks are found be advantageous if individuals share mynah (Acridotheres tristis), rufous tree pie swirling around nesting grounds to feed information about the location of (Dendroci a vagabunda) and black drongo the eggs and the young ones. ephemeral patches of food (Krebs 1974). (Dicrurus macrocercus) form a group in the For instance, when the temperature in On 1st July 2014 in Kasargode same location at the same time especially Andaman in the year 2012 during the district of Kerala a tree belonging to before heavy rains. The high pitched cries month of February averaged 30 degrees acacia species was found fallen horizontal of babblers and mynahs and their frenzied Celsius during day with 70% atmospheric on the ground due to the previous night’s moves from one branch to another before humidity and night temperatures 22 stormy rain. A group of birds belonging they lunge down to the ground to forage degrees Celsius with 20% atmospheric to different species were found encircling is gawked over by the black drongo. The humidity, reddish brown berries started a motionless object on the tree trunk – a drongo dives down swiftly and robs the appearing on the branches of a peepal spotted owlet (Athene brama). insects from the babblers. In this situation tree. It was located by birds such as house the feeding effi ciency of one species gets These fruits attracted all the crow (Corvus splendens), black hooded reduced due to the presence of other frugivorous birds such as Asian fairy blue oriole (Oriolus xanthornus), common myna species. bird (Irena puella), Asian koel (Eudynamys (Acridotheres tristis), red whiskered bulbul A similar kind of interference in scolopacea ), green imperial pigeon (Ducula (Pycnonotus jocosus), loten’s sunbird feeding between species was seen in an aenea), black headed bulbul (Pycnonotus (Nectarinia lotenia) male and female all open forest of Andaman where a greater fuscofl avescens), oriental cuckoo (Cuculus with their characteristic chattering sounds racket-tailed drongo intimidated a large saturatus) to the tree. Thus the resources and they seemed restless. The owlet kept cuckoo shrike (Coracina macei) with were shared in a gregarious manner. staring at these birds that were chirping harsh threatening calls making the less Such mixed species group is transient as consistently. It subsequently fl uttered off dominant cuckoo shrike drop down its the fruiting season gets over within a few to a distant tree. prey and fl y away. days. So, until now we had heard that A similar kind of interaction was Warding Off Brood Parasites “birds of a feather fl ock together”. also observed in grassland habitats However, it is now apparent that “birds of Brood parasites are organisms that rely where insect-eating birds like chestnut different feathers fl ock together as well”. headed bee-eater (Merops leschenaultia on others to raise their young (David andamanensis), blue tailed bee-eater Attenborough, The Life of Birds 1998). M.C. Bindya is a Post Graduate Teacher in Biology, (Merops philippinus), and brown shrike Cuckoos are considered brood parasites Jawahar Navodaya Vidyalaya, Shivaragudda, (Lanius cristatus lucionensis) were seen for this reason. The host birds may range Mandya District, Karnataka-571419; perched close to each other on street wires from birds as small as sun birds to larger Email: [email protected] 23 Science Reporter, MAY 2016