Florian Möllers / Mallard (Anas platyrhynchos), female nesting in window box of a 4th floor flat, Berlin, Germany, June

Florian Möllers / Photographer Florian Mollers having breakfast beside a female Mallard (Anas platyrhynchos) nesting in window box of a 4th floor flat, Berlin, Germany, June. Model released

Nick Upton / Nick Upton setting up a remote camera on an extension roof to photograph Common swifts (Apus apus) coming and going from a nest box under the eaves of a cottage, Hilperton, Wiltshire, UK, June 2016. M...

Nick Upton / Remote camera set up on an extension roof to photograph Common swifts (Apus apus) coming and going from a nest box under the eaves of a cottage, Hilperton, Wiltshire, UK, June 2016.

Nick Upton / Common swift (Apus apus) flying to its nest in a Swift nest box in the belfry of All Saints Church, Worlington, Suffolk, UK, July.

Edwin Giesbers / Wood pigeon (Columba palumbus) nesting in window box of balcony. The Netherlands.

Nick Upton / Common swift (Apus apus) call playback system positioned and turned on successfully by Roger Becket and Peter Grayshon below a nest box they've just fitted into a louvred window in the bell tower of H...

Nick Upton / Common swift (Apus apus) nest box fitted by Roger Becket and Peter Grayshon into a louvred window in the bell tower of Holy Trinity church, Bradford-on-Avon, Wiltshire, UK, June.

Nick Upton / Common swift (Apus apus) nest box fitted by Roger Becket and Peter Grayshon into a louvred window in the bell tower of Holy Trinity church, Bradford-on-Avon, Wiltshire, UK, June.

Nick Upton / Common swift (Apus apus) nest box fitted by Roger Becket and Peter Grayshon into a louvred window in the bell tower of Holy Trinity church, Bradford-on-Avon, Wiltshire, UK, June.

Nick Upton / Common swift (Apus apus) nest box fitted by Roger Becket and Peter Grayshon into a louvred window in the bell tower of Holy Trinity church, Bradford-on-Avon, Wiltshire, UK, June.

Nick Upton / Common swift (Apus apus) nest box fitted by Roger Becket and Peter Grayshon into a louvred window in the bell tower of Holy Trinity church, Bradford-on-Avon, Wiltshire, UK, June.

Nick Upton / Common swift (Apus apus) call playback system positioned below a nest box just fitted by Roger Becket and Peter Grayshon into a louvred window in the bell tower of Holy Trinity church, Bradford-on-Avo...

Nick Upton / Peter Grayshon replaces inspection covers to a Common swift (Apus apus) nest box he's just helped to attach to a louvred window in the bell tower of Holy Trinity church, Bradford-on-Avon, Wiltshire, U...

Gary K. Smith / Venetian window box with succulents and cyclamen Venice, Italy, April.

Gary K. Smith / Window box with Nasturtiums, Curry Plant and Succulents in Venice, Italy. April.

Gary K. Smith / Potted Pelagoniums in window box Venice, Italy, April.

Gary K. Smith / Window box with Nasturtiums, Curry Plant and Succulents, Venice, Italy, April.

Eric Medard / Kestrel (Falco tunninculus) two young birds perched on window of nest box, France, June

Eric Medard / Kestrel (Falco tunninculus) two young birds perched on window of nest box, France, June

Eric Medard / Kestrel (Falco tunninculus) on nest box window, France, June

Florian Möllers / Mallard (Anas platyrhynchos), female nesting in window box of a 4th floor flat, Berlin, Germany, June

Florian Möllers / Mallard (Anas platyrhynchos), female nesting in window box of a 4th floor flat, Berlin, Germany, June

Florian Möllers / Woman rescues the duckling of a Mallard (Anas platyrhynchos) nesting in window box of a 4th floor flat, female duck watching, Berlin, Germany, June

Florian Möllers / Mallard (Anas platyrhynchos), female nesting in window box of a 4th floor flat, Berlin, Germany, June

Florian Möllers / Mallard (Anas platyrhynchos), female nesting in window box of a 4th floor flat, Berlin, Germany, June

Florian Möllers / Two women rescue the ducklings of a Mallard (Anas platyrhynchos) nesting in window box of a 4th floor flat, Berlin, Germany, June

Florian Möllers / Mallard (Anas platyrhynchos), female nesting in window box of a 4th floor flat, Berlin, Germany, June

Florian Möllers / Man photographing a female Mallard (Anas platyrhynchos) nesting in window box of a 4th floor flat, Berlin, Germany, June

Florian Möllers / Woman rescues the duckling of a Mallard (Anas platyrhynchos) nesting in window box of a 4th floor flat, Berlin, Germany, June

Florian Möllers / Man taking photo with mobile phone of female Mallard (Anas platyrhynchos) nesting in window box of a 4th floor flat, Berlin, Germany, June

Jouan & Rius / Traditional timber-frame house with shutters and window box, Kaysersberg village, Upper Rhine, Alsace, France, May 2009

Fabio Liverani / Lesser kestrel (Falco naumanni) nesting in a window box on a balcony with a woman hanging up washing, Matera, Basilicata, Southern Italy

Fabio Liverani / Lesser kestrel (Falco naumanni) nesting in window box, Matera, Basilicata, Southern Italy

Juan Manuel Borrero / House with balcony in Santa Cruz, La Palma, Canary Islands 2007

John F.Burton / Swallowtail butterfly on window box flowers. Near Heidelberg, Germany

Charlie Hamilton James / Kestrel with chicks in London window box, England

Roberto Rinaldi / Statue of Madonna and Jesus child, Burano, Italy.

Roberto Rinaldi / Blue house, Burano, Italy.

Roberto Rinaldi / Decorated window boxes, Burano, Italy.

Oriol Alamany / Peregrine falcon (Falco peregrinus) perched on top of nest box, on Torres Porta Fira office building, L'Hospitalet de Llobregata, Catalonia, Spain. May.