Aerial Environment.

For most birds flying is a means of getting about, moving to different geographical areas of the world in search of food or perhaps simply avoiding predators but for some birds flying is an absolutely essential part of how they find and take their food.

1. Flying Insectivores (2.0%).

Aerial insectivores feed on flying insects whilst on the wing:-

• The nature of the land or water features over which the birds fly is important from the point of view of insect availability.
• Sub-habitats can be broadly defined in terms of geographic regions

Agile, high fliers, cling rather than perch (1.0%).

World-wide, except polar regions and deserts - Swifts (100 species) have such short legs they can hardly perch at all - they use their feet to cling to surfaces but can't feed at the same time. Consequently they have to feed on flying insects while they are themselves in flight. They cannot gather nest-making materials so they use their own saliva to make nests on vertical surfaces and even on the roofs of caves. In fact the place they choose to nest is one of the factors which enable one to differentiate one species from another.

Good fliers, can perch (1.0%).

World-wide, especially Africa and Central / Southern America - Swallows and Martins (86 species) - nest in a similar manner to the Swifts but are able to collect mud rather than using saliva. Habitats tend to be over waterways and marshy land where insects are plentiful. They tend to take insects at a lower height than the Swifts.

Australia and New Guinea - Wood Swallows (11 species) are endemic, aerial insectivores, favouring areas above eucalyptus forest and woodland. They have considerable endurance and can stay aloft for many hours.

Old World birds found mainly in Africa, Australia and Europe - Pratincoles (8 species) - favour wetland and inland water areas. They are ground nesters and tend to feed at dawn and dusk.

2. Flying Carnivores (6.4%).

Birds which eat flesh are at the top of the food chain and their habitat is wherever they want it to be. The ability to fly high and fast, coupled with excellent sight and sense of smell enables these birds to find food over large areas of the land below. For these birds sub-habitats can be defined by the type of land the prey is in, the geographic location and the searching and feeding technique employed.

Commonly referred to as Birds of Prey but we also use the term Raptor. I believe definitions should be used with care so it's worth looking at what we mean when we talk about these birds:-

Raptor is a term used to describe a bird which seizes prey or takes it by force. It is generally used for Birds of Prey like Eagles, Hawks, Falcons, Vultures, etc. Some would also describe Owls using this term but others would not. In the world of birds there are always exceptions; the Palm-nut Vulture does not hunt live prey but it will take carrion.

Prey is small, live animals, carcasses or carrion usually on the ground. I would include birds in nests, perched and even in flight. Although fish is also flesh it is only available live in aquatic environments which are not usually regarded as habitats for birds of prey. Dead fish however would seem to be regarded as carrion.

Characteristics and behaviour which can be observed include talons on their feet and hooked beaks, often large size and aggressive behaviour. In Australia the Currawongs and Butcherbirds can be about the size of a Sparrowhawk but are not generally regarded as birds of prey. They have difficulty in holding small animals with their feet so they generally wedge it in a tree fork or impale it on a thorn. The Andean Condor also has week feet but most people would call it a Bird of Prey.

On the other hand the large Frigatebirds, which are generally regarded as sea and ocean birds, are piratical, seizing prey from other seabirds. Their large size and hooked beak would surely meet definitions of Birds of Prey and Raptors but I have never seen them described as such.

Bearing in mind the foregoing comments I use the following definitions:-

Aerial Carnivores - Diurnal (4.4%).

Hunters (3.2%).

Large, meat eating birds which hunt by day using senses such as sight and smell and which catch live prey and sometimes feed on carrion. I would include the Palm-nut Vulture which takes dead fish but exclude Frigatebirds and other ocean or sea fish eaters. I would therefore include the 317 species in families Cathartidae, Falconidae and Accipitridae.

Habitats for these birds are almost any where they want them to be. Prey can be found almost anywhere on the ground in the form of live animals or carrion. Birds in flight or perched can be prey for larger or more robust raptors.

Opportunistic feeders (1.2%).

Many of these birds have evolved to become scavengers and will also take carrion. The 123 species of Corvids include Crows (33), Magpies (14), Treepies (10), Ravens (9) as well as Jackdaws, Choughs and Nutcrackers (2 each) and the Rook (1). The 50 Jays are mainly New World birds. I am not comfortable with including Nutcrackers and Jays here and I will probably move them when I have considered them in more detail.

Aerial Carnivores - Nocturnal (2.0%).

Meat eating birds which hunt live prey by night using their exceptional sight and hearing. These are the 202 species of Owls in the order Strigiformes.