ML618380039
投稿者
日付
場所
- 年齢
- 指定なし
- 性別
- 指定なし
観察結果の詳細
This species reaches the northern limit of its range in southern Texas where it appears to be increasing. Prior to 1950 it was considered rare. Resembling an oversized male Hooded Oriole, it is the largest oriole in the US. Texas birds are the smaller more brightly colored subspecies "I. g. tamaulipensis" formerly known as Lichtenstein's Oriole. Males and females look alike. They remain paired throughout the year and are resident. Why do migratory orioles show a strong sexual dimorphism while tropical non-migratory species such as this do not? I understand that dimorphism is advantageous to migratory birds who must find new mates each year, while resident species that remain paired throughout the season do not find selective advantage in having males differ from females. But why do both sexes have a bright male-like plumage when predator avoidance should favor drab appearance? Any thoughts?
テクニカル・インフォメーション
- モデル
- Canon PowerShot SX70 HS
- ISO
- 250
- 焦点距離
- 247 mm
- フラッシュ
- Flash did not fire
- Fストップ
- f/6.5
- シャッタースピード
- 1/400 sec
- 大きさ
- 1024 pixels x 853 pixels
- オリジナルのファイルサイズ
- 365.1 KB