The changes birds experience in their appearance during the breeding season sometimes include a partial molt, resulting in a more colorful or ornate plumage in the spring. In addition, some species, such as those in the Heron family (herons, egrets and bitterns), undergo changes in the color of their bills, legs, feet and lores (area between eye and bill) during their brief period of courtship. As an example, Snowy Egrets (pictured), during most of the year, have featherless yellow patches of skin, or lores, at the base of their bill and greenish-yellow feet, but in the spring, their lores turn red and their feet a bright yellow-orange.
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American Bitterns typically nest in tall, standing cattails, rushes and sedges, where they are well concealed. Like most birds, male bitterns use their voice to attract a female and to stake out their territory. Dense marshes present a challenge when it comes to being heard, however. American Bitterns overcome this challenge by having a very low-frequency call, which is audible at great distances in dense marsh vegetation. Once you’ve heard a bittern’s call, you’ll never forget it. It is very deep, and has three syllables – “oong-ka-choonk” – which are preceded by clicks and gulps. The bittern makes this call multiple times by inflating his esophagus while contorting himself quite violently. A female American Bittern couldn’t help but be impressed. (You can hear a bittern calling by visiting Cornell’s site, http://www.allaboutbirds.org/guide/american_bittern/sounds .