John Shaw / Yellow warbler (Setophaga petechia aureola) on lava rocks. Isabela Island, Galapagos. May.

Paul Hobson / Wood warbler (Phylloscopus sibilatrix) singing whilst perched on branch, silhouetted at dawn. Sheffield, England, UK. May.

Markus Varesvuo / Wood Warbler (Phylloscopus sibilatrix), Estonia, May 2005

Fergus Gill / 2020VISION / Wood Warbler (Phylloscopus sibilatrix) singing from an oak tree, Atlantic Oakwoods of Sunart, Scotland, May.

Fergus Gill / 2020VISION / Wood warbler (Phylloscopus sibilatrix) singing from a lichen covered branch, Atlantic Oakwoods of Sunart, Scotland, May.

Andy Rouse / 2020VISION / Wood warbler (Phylloscopus sibilatrix) in flight in sesile oak forest, Wales, UK, May. 2020VISION Book Plate.

Andy Rouse / 2020VISION / Wood Warbler (Phylloscopus sibilatrix) singing from perch. Wales., April.

Andy Rouse / 2020VISION / Wood Warbler (Phylloscopus sibilatrix) juvenile perched. Wales, April. Did you know? Despite inhabiting woodlands, wood warblers prefer to nest on or close to the ground.

Markus Varesvuo / Wood warbler (Phylloscopus sibilatrix) on branch singing, Estonia, May

Andy Rouse / Wood Warbler (Phylloscopus sibilatrix) perched on branch in Oak (Quercus) woodlands, Snowdonia NP, Wales, UK, May.

Andy Rouse / Wood Warbler (Phylloscopus sibilatrix) perched on branch in Oak (Quercus) woodlands, Snowdonia NP, Wales, UK, May.

Andy Rouse / Wood Warbler (Phylloscopus sibilatrix) adult displaying begging / courtship behaviour and calling, perched on branch in Oak (Quercus) woodlands, Snowdonia NP, Wales, UK, May.

Andy Rouse / Wood Warbler (Phylloscopus sibilatrix) close up, perched on branch in Oak (Quercus) woodlands, Snowdonia NP, Wales, UK, May.

Andy Rouse / Wood Warbler (Phylloscopus sibilatrix) perched on branch in Oak (Quercus) woodlands, Snowdonia NP, Wales, UK, May.

Andy Rouse / Wood Warbler (Phylloscopus sibilatrix) perched on branch in Oak (Quercus) woodlands, Snowdonia NP, Wales, UK, May.

Alan Williams / Wood warbler (Phylloscopus sibilatrix) singing in woodland, North Wales, UK, May

Paul Hobson / Wood warbler (Phylloscopus sibilatrix) male singing, perched on branch in morning light. Sheffield, England, UK. May.

Bruno D'Amicis / Wood warbler (Phylloscopus sibilatrix) singing on tree branch in old-growth Beech (Fagus sylvatica) forest. UNESCO World Heritage Site. Abruzzo, Lazio and Molise National Park, Italy. June

David Tipling / Spotted flycatcher (Muscicapa striata) in song North Norfolk, England, UK. May

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) sitting in tree in Jack Pine habitat. Michigan, USA. July.

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) male carrying food for young, Michigan, USA. July.

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) sitting on Jack Pine carrying food for her young, Michigan, USA, July.

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) male with nano tag, sitting on Jack pine collecting prey for young.

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) female in jack pine carrying food for young. Michigan, USA, July.

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) female in Jack pine habitat bringing food to her nest, Michigan, USA, July.

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) nano tagged male sitting in Jack pine, Michigan, USA, July.

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) male singing perched in Jack pine near nest. Michigan, USA, July.

Karine Aigner / Map of Kirtland's warbler (Setophaga kirtlandii) nests drawn by researcher, in Jack pine forest habitat. Michigan, USA, July 2017.

Karine Aigner / Portrait of a female Kirtland's warbler (Setophaga kirtlandii) a Jack pine tree. Michigan, USA, July 2017.

Karine Aigner / Portrait of a female Kirtland's warbler (Setophaga kirtlandii) in Jack pine tree. Michigan, USA, July 2017.

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) nest, Michigan, USA, July.

Karine Aigner / Researcher pulls back the undergrowth to reveal the ground nest of a Kirtland's warbler (Setophaga kirtlandii) family, Michigan, USA, July 2017.

Karine Aigner / Portrait of Nathan Cooper checking for Kirtland's warblers (Setophaga kirtlandii) Michigan, USA, July 2017.

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) chick sitting on three failed eggs. Michigan, USA, July 2017.

Karine Aigner / Kirtland's warbler (Setophaga kirtlandii) male on black background. Michigan, USA, July 2017.

Karine Aigner / Scientist Nathan Cooper refiting a male Kirtland's warbler (Setophaga kirtlandii) with a new nano tag, Michigan, USA, July.

Karine Aigner / Portrait of a male Kirtland's warbler (Setophaga kirtlandii) held up in scientists hands, in breeding grounds of Jack Pine habitat. Michigan, USA, July 2017.

Karine Aigner / Biologist Nathan Cooper holding male Kirtland's warbler (Setophaga kirtlandii) before replacing previous nano tag with a new one. Michigan, USA. July 2017.

Karine Aigner / Biologist Nathan Cooper taking measurements from male Kirtland's warbler (Setophaga kirtlandii) before replacing previous nano tag with a new one.Michigan, USA. July 2017.

Karine Aigner / Scientist Nathan Cooper holding a baby Kirtland's warbler (Setophaga kirtlandii) Michigan, USA, July 2017.

Karine Aigner / Wild sage / Buttonsage (Lantana involucrata) on black background, a favourite food of the Kirtland's Warbler (Setophaga kirtlandii), Cat Island, Bahamas.

Karine Aigner / Scientist Nathan Cooper adjusting nano-tag put on a Kirtland's warbler (Setophaga kirtlandii) Cat Island, Bahamas, April 2017.

Karine Aigner / Scientist Nathan Cooper adjusting nano-tag that is being put on a Kirtland's warbler (Setophaga kirtlandii) Cat Island, Bahamas, April 2017.

Karine Aigner / Scientist Nathan Cooper writing down data after he weighs and measures a Kirtland's warbler (Setophaga kirtlandii) Cat Island, Bahamas, April 2017.

Karine Aigner / Scientist Nathan Cooper takes a feather sample from an endangered Kirtland's Warbler (Setophaga kirtlandii) Cat Island, Bahamas, April 2017.

Karine Aigner / Scientist Nathan Cooper blowing feathers out of the way while measuring the size of the pectoral muscle of a Kirkland's Warbler (Setophaga kirtlandii) during research. Cat Island, Bahamas. April 2...

Karine Aigner / Scientist Nathan Cooper detangles an endangered Kirtland's Warbler (Setophaga kirtlandii) from the mist net. This bird was caught for tagging during research into migration and behaviour. Cat Isla...

Karine Aigner / Kirtland's warblers (Setophaga kirtlandii) fecal sample blots. Cat Island, Bahamas. April 2017.

Karine Aigner / Scientists Nathan Cooper measures the beak of an endangered Kirtland's warbler (Setophaga kirtlandii) Cat Island, Bahamas. April 2017.

Karine Aigner / Scientists Nathan Cooper and Stephen Caird play the call of a Kirtland's Warbler (Setophaga kirtlandii) to elicit a response from wild warblers. This is so they know where to set up a mist net to...

Karine Aigner / Scientist noting GPS points are noted so that field assistants can find Kirkland's warblers (Setophaga kirtlandii) using nano-transmitters data. Cat Island, Bahamas. April 2017.

Karine Aigner / Nathan Cooper and Stephen Caird play the call of a Kirtland's Warbler (Setophaga kirtlandii) to elicit a response from wild warblers. This is so they know where to set up a mist net to capture the...

Karine Aigner / Scientist Nathan Cooper at the Smithsonian Migratory Bird Center holding Kirtland's warbler (Setophaga kirtlandii) during tagging study. CAt Island, Bahamas. April 2017.

Karine Aigner / Scientist Nathan Cooper at the Smithsonian Migratory Bird Center holding Kirtland's warbler (Setophaga kirtlandii) during tagging study. CAt Island, Bahamas. April 2017.

Karine Aigner / Blood sample collecting from Kirkland's warblers (Setophaga kirtlandii) Cat Island, Bahamas. April 2017.

Karine Aigner / Scientist Nathan Cooper puts a nano-tag on a Kirtland's warbler (Setophaga kirtlandii) Cat Island, Bahamas. April 2017.

Karine Aigner / Scientist Nathan Cooper at the Smithsonian Migratory Bird Center holding Kirtland's warbler (Setophaga kirtlandii) during tagging study. CAt Island, Bahamas. April 2017.

Karine Aigner / Scientist Nathan Cooper measuring the size of the pectoral muscle of a Kirkland's Warbler (Setophaga kirtlandii) during research. Cat Island, Bahamas. April 2017.

Karine Aigner / Nathan Cooper and Stephen Caird play the call of a Kirtland's Warbler (Setophaga kirtlandii) to elicit a response from wild warblers. This is so they know where to set up a mist net to capture the...

Karine Aigner / Scientist Nathan Cooper detangles and endangered Kirtland's Warbler (Setophaga kirtlandii) from the mist net. This bird was caught for tagging during research into migration and behaviour. Cat Isl...

Karine Aigner / Northern waterthrush (Parkesia noveboracensis) at waters edge, Cat Island, Bahamas.

Karine Aigner / Portrait of a Myrtle warbler, (Dendroica coronata coronata) with white background, Block island, Rhode Island, USA. Bird caught during scientific research.

Karine Aigner / Portrait of a Orange-crowned warbler, (Vermivora celata) with white background, Block island, Rhode Island, USA. Bird caught during scientific research.

Karine Aigner / Portrait of a Palm warbler (Setophaga palmarum) with white background, Block island, Rhode Island, USA. Bird caught during scientific research.

Eladio Fernandez / Olive-capped warbler (Setophaga pityophila) Sierra del Rosario, Cuba.

Richard Du Toit / Spotted Flycatcher (Muscicapa striata) Mountain Zebra National Park, Eastern Cape Province, South Africa.

Sue Flood / Emperor penguin chick flapping its wings (3 of 3) at Snow Hill Island rookery, Weddell Sea, Antarctica. November.

Sue Flood / Aerial of icebreaker Kapitan Khlebnikov, Snow Hill Island, Weddell Sea, Antarctica, November 2009.

Jeff Foott / Yellow warbler (Dendroica petechia) at Yellow-Bellied Sapsucker site (Sphyrapicus varius) damage in tree to eat sap. Sapsuckers damages trees trunks to feed on sap. Teton National Park, Wyoming, USA....

Dave Bevan / Wood warbler (Phylloscopus sibilatrix) displaying and calling from the branches of an Oak tree (Quercus), Carmarthenshire, Wales, UK, May.

Dave Bevan / Wood warbler (Phylloscopus sibilatrix) displaying, Carmarthenshire, Wales, UK, May.

Nick Hawkins / Common yellow throat (Geothlypis trichas) male, singing, Anchorage Provincial Park, Grand Manan Island, New Brunswick, Canada, June.

Barry Mansell / Prothonotary warbler (Protonotaria citrea) male, Florida,USA

Barry Mansell / Prothonotary warbler (Protonotaria citrea) male, Florida,USA

Barry Mansell / Prothonotary warbler (Protonotaria citrea) male, Florida,USA

Barry Mansell / Pine warbler (Dendroica pinus) male, North Florida, USA, February.

Phil Savoie / Yellow warbler (Dendroica petechia) male singing. Bozeman, Montana, USA.

Phil Savoie / Yellow warbler (Dendroica petechia) male singing. Bozeman, Montana, USA.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana.

Phil Savoie / Yellow warbler (Dendroica petechia) male, Bozeman, Montana, USA.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana.

Phil Savoie / Yellow warbler (Dendroica petechia) male, Bozeman, Montana, USA.

Phil Savoie / Yellow warbler (Dendroica petechia) male singing. Bozeman, Montana, USA. June.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana, June.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana, USA, June.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana, USA, June.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana.

Phil Savoie / Yellow warbler (Dendroica petechia) collecting nesting material from Bulrush cattail (Typha sp) Bozeman, Montana, USA, June.

Phil Savoie / Yellow warbler (Dendroica petechia) male hunting midges, Bozeman, Montana, USA. June.

Phil Savoie / Yellow warbler (Dendroica petechia) hunting insects, Madison River, Bozeman, Montana, USA. June.