Gerrit Vyn / Adult white-striped morph White-throated Sparrow (Zonotrichia albicollis) perched on branch, in breeding plumage. Tompkins County, New York, USA, May.

Gerrit Vyn / Adult male Willow Ptarmigan (Lagopus lagopus) in breeding or courtship plumage, perched on a branch, Seward Peninsula, Alaska, USA, May.

Gerrit Vyn / Adult male Mourning Warbler (Oporornis philadelphia) perched on branch, in breeding plumage. Tompkins County, New York, USA, May.

Gerrit Vyn / Adult male Common Yellowthroat (Geothlypis trichas) perched on branch, in breeding plumage. Tompkins County, New York, USA, May.

Gerrit Vyn / Adult male Blackburnia Warbler (Dendroica fusca)perched on branch, in breeding plumage. Tompkins County, New York, USA, May.

Gerrit Vyn / Canada Warbler (Cardellina canadensis) male in breeding plumage with a caterpillar prey, Tompkins County, New York, USA, May.

Gerrit Vyn / Male Pine Warbler (Dendroica pinus) perched on branch, in breeding plumage. Tompkins County, New York, USA, May.

Gerrit Vyn / Adult male Chestnut-sided Warbler (Dendroica pensylvanica) perched on branch, in breeding plumage. Tompkins County, New York, USA, May.

Gerrit Vyn / Adult male Blue-winged Warbler (Vermivora pinus) in breeding plumage, perched in Lichen covered branch. Tompkins County, New York, USA, May.

Gerrit Vyn / Singing male Black-throated Green Warbler (Dendroica virens) in breeding plumage, perched on branch. Tompkins County, New York, USA, May.

Gerrit Vyn / Adult male Prairie Warbler (Dendroica discolor) in breeding plumage, perched on branch. Tompkins County, New York, USA, May.

Gerrit Vyn / Adult male Pine Warbler (Dendroica pinus) in breeding plumage. Spring, Tompkins County, New York. USA

Gerrit Vyn / Male Bobolink (Dolichonyx oryzivorus) in breeding plumage. Tompkins County, New Jersey, USA

Gerrit Vyn / White-throated Sparrow (Zonotrichia albicollis) in white-striped morph breeding plumage. Tompkins County, New York, USA

Gerrit Vyn / Couch's Kingbird (Tyrannus couchii). Starr County, Texas.

Marie Read / Scarlet Tanager (Piranga olivacea), male in breeding plumage perched amid beech leaves in spring, New York, USA

Marie Read / Scarlet Tanager (PIranga olivacea), male in breeding plumage perched amid spring foliage, New York, USA

George Sanker / Wood duck (Aix sponsa) drake in breeding plumage at the base of tree, Walpole, New Hampshire, New England, USA, Spring

Donald M. Jones / Yellow-rumped Warbler (Setophaga coronata) male in breeding plumage calling, western Montana

Chris O'Reilly / Dunlin (Calidris alpina) adult in breeding plumage, shore of a lake, Peak District NP, Derbyshire, UK, spring

Donald M. Jones / Lesser Yellowlegs (Tringa flavipes) in spring plumage wading in lake, central Montana

Bruno D'Amicis / Thick-billed lark (Ramphocoris clotbey) adult male in spring plumage. Rare breeder in mountain steppes and dry habitats of Southern Morocco. NW Africa

Bruno D'Amicis / Thick-billed lark (Ramphocoris clotbey) adult male in spring plumage. Rare breeder in mountain steppes and dry habitats of Southern Morocco. NW Africa

Roger Powell / Flock of Red Knot {Calidris canutus} in breeding plumage flying over sea on spring migration, Varanger, Norway

David Kjaer / Ptarmigan (Lagopus mutus) female in spring plumage, Cairngorms, Scotland, UK

David Kjaer / Lesser Yellowlegs (Tringa flavipes) on shore in spring plumage, Texas, USA

Roger Powell / Blue Tit {Parus caeruleus} with spring plumage, Northumberland, UK

Roger Powell / Blue Tit {Parus caeruleus} with spring plumage, Northumberland, UK

Roger Powell / Blue Tit {Parus caeruleus} with spring plumage, Northumberland, UK

Chris Gomersall / Northern wheatear (Oenanthe oenanthe), adult male in spring plumage on farm midden heap. Hertfordshire, England. April.

Chris Gomersall / Common starling (Sturnus vulgaris), male adult in spring plumage catching insects on farm midden heap. Hertfordshire, England. April.

Chris Gomersall / Common starling (Sturnus vulgaris), adult in spring plumage catching insects on farm midden heap. Hertfordshire, England. April.

Chris Gomersall / Moorhen (Gallinula chloropus) adult in spring plumage. North Norfolk, England. March.

Chris Gomersall / Northern wheatear (Oenanthe oenanthe), adult male in spring plumage on farm midden heap. Hertfordshire, England. April.

Chris Gomersall / Northern wheatear (Oenanthe oenanthe), adult male in spring plumage on farm midden heap. Hertfordshire, England. April.

Chris Gomersall / Yellow wagtail (Motacilla flava flavissima), male in spring plumage on farm midden heap. Hertfordshire, England. April.

David Kjaer / Black Grouse (Tetrao terix) males displaying / fighting on lek, spring, Deeside, Scotland UK

David Kjaer / Two male Black Grouse (Tetrao terix) displaying on lek, spring, Deeside, Scotland UK

David Kjaer / Male Black Grouse (Tetrao terix) displaying on spring lek, Deeside, Scotland UK

David Kjaer / Male Black Grouse (Tetrao terix) displaying on spring lek, Deeside, Scotland UK

David Kjaer / Male Black Grouse (Tetrao terix) displaying on spring lek, Deeside, Scotland UK

David Kjaer / Male Black Grouse (Tetrao terix) displaying at spring lek, Deeside, Scotland UK

David Kjaer / Male Black Grouse (Tetrao terix) displaying and calling on spring lek, Deeside, Scotland UK

David Kjaer / Male Black Grouse (Tetrao terix) displaying on spring lek, Deeside, Scotland UK

Chris Gomersall / Mandarin duck (Aix galericulata) male or drake in spring plumage, Devon, UK

Rolf Nussbaumer / Long-billed Dowitcher {Limnodromus scolopaceus} wading with spring plumage, Welder Wildlife Refuge, Sinton, Texas, USA.

Rolf Nussbaumer / Stilt Sandpiper {Calidris himantopus} adult with spring plumage in water, Welder Wildlife Refuge, Sinton, Texas, USA.

John Cancalosi / Golden plover calling, Scotland (Pluvialis apricaria), Shetland Islands, UK Breeding plumage

DAVID TIPLING / Starling (Sturnus vulgaris). UK, Europe

DAVID TIPLING / Starling (Sturnus vulgaris). UK, Europe

Chris O'Reilly / Common starling (Sturnus vulgaris) male in breeding plumage. England, UK, Europe

LYNN M. STONE / Brown pelican with fish in beak {Pelecanus occidentalis} Spring plumage, SW Florida USA

Thomas Lazar / Snowy egret breeding display (Egretta thula) Florida, USA.