The swamp resembles a big dining-table for the birds. Wild grape-vines clamber to the tops of the highest trees, spreading umbrella-wise over the branches, and their festooned floating trailers wave as silken fringe in the play of the wind. The birds loll in the shade, peel bark, gather dried curlers for nest material, and feast on the pungent fruit. They chatter in swarms over the wild-cherry trees, and overload their crops with red haws, wild plums, papaws, blackberries and mandrake. The alders around the edge draw flocks in search of berries, and the marsh grasses and weeds are weighted with seed hunters. The muck is alive with worms; and the whole swamp ablaze with flowers, whose colours and perfumes attract myriads of insects and butterflies.

2 Wild creepers flaunt their red and gold from the treetops, and the bumblebees and humming-birds make common cause in rifling the honey-laden trumpets. The air around the wild-plum and redhaw trees is vibrant with the beating wings of millions of wild bees, and the bee-birds feast to gluttony. The fetid odours of the swamp draw insects in swarms, and fly-catchers tumble and twist in air in pursuit of them.

3 Every hollow tree homes its colony of bats. Snakes sun on the bushes. The water folk leave trails of shining ripples in their wake as they cross the lagoons. Turtles waddle clumsily from the logs. Frogs take graceful leaps from pool to pool. Everything native to that section of the country-underground, creeping, or a-wing--can be found in the Limberlost; but above all the birds. Dainty green warblers nest in its tree-tops, and red-eyed vireos choose a location below. It is the home of bell-birds, finches, and thrushes. There are flocks of blackbirds, grackles, and crows. Jays and catbirds quarrel constantly, and marsh-wrens keep up never-ending chatter. Orioles swing their pendent purses from the branches, and with the tanagers picnic on mulberries and insects. In the evening, night-hawks dart on silent wing; whippoorwills set up a plaintive cry that they continue far into the night; and owls revel in moonlight and rich hunting. At dawn, robins wake the echoes of each new day with the admonition, "Cheer up! Cheer up!" and a little later big black vultures go wheeling through cloudland or hang there, like frozen splashes, searching the Limberlost and the surrounding country for food. The boom of the bittern resounds all day, and above it the rasping scream of the blue heron, as he strikes terror to the hearts of frogdom; while the occasional cries of a lost loon, strayed from its flock in northern migration, fill the swamp with sounds of wailing.

4 Flashing through the tree-tops of the Limberlost there are birds whose colour is more brilliant than that of the gaudiest flower lifting its face to light and air. The lilies of the mire are not so white as the white herons that fish among them. The ripest spray of goldenrod is not so highly coloured as the burnished gold on the breast of the oriole that rocks on it. The jays are bluer than the calamus bed they wrangle above with throaty chatter. The finches are a finer purple than the ironwort. For every clump of foxfire flaming in the Limberlost, there is a cardinal glowing redder on a bush above it. These may not be more numerous than other birds, but their brilliant colouring and the fearless disposition make them seem so. Which is the BEST inference you can make about most birds in the passage?
A) That they are most concerned with finding plenty of food
B) That they are most concerned with defending their territory
C) That they are most concerned with producing beautiful songs
D) There are no valid inferences to be made about the birds in this passage.