Salida de campo a Laguna de Duero (Valladolid) la mañana del 22 de febrero de 1952, de la que se observó la elevada actividad de los topillos (Microtus sp.), la ausencia de ranas (sin diferenciar especies) y se anotaron observaciones sobre las siguientes aves: Acrocephalus arundinaceus (Carricero tordal), Alauda arvensis (Alondra común), Anas crecca (Cerceta común), Anas penelope (Silbón europeo), Anas platyrhynchos (Ánade azulón), Ardea cinerea (Garza real), Carduelis carduelis (Jilguero), Carduelis chloris (Verderón común), Clamator glandarius (Críalo europeo), Columba palumbus (Paloma torcaz), Corvus corone (Corneja negra), Corvus frugilegus (Graja), Corvus monedula (Grajilla, llamada Coloeus por el autor), Dendrocopos sp. (Pico, llamado, Dryobates sp. por el autor), Emberiza cia (Escribano montesino), Emberiza cirlus (Escribano soteño), Emberiza schoeniclus (Escribano palustre), Fringilla sp. (Pinzón), Gallinago gallinago (Agachadiza común, llamada Capella gallinago por el autor), Gallinula chloropus (Gallineta común), Larus ridibundus (Gaviota reidora), Limosa limosa (Aguja colinegra), Lophophanes cristatus (Herrerillo capuchino, llamado Parus cristarus por el autor), Lullula arborea (Totovía), Lymnocryptes minimus (Agachadiza chica), Miliaria calandra (Triguero, llamada Emberiza calandra por el autor), Motacilla alba (Lavandera blanca), Motacilla cinerea (Lavandera cascadeña), Motacilla sp. (Lavandera), Parus major (Carbonero común), Passer montanus (Gorrión molinero), Periparus ater (Carbonero Garrapinos, llamado Parus ater por el autor), Pica pica (Urraca), Picus viridis (Pito real), Podiceps sp. (puede referirse a P.cristatus, P.nigricollis o Tachybaptus ruficollis), Regulus sp. (Reyezuelo), Saxicola torquata (Tarabilla común), Serinus serinus (Verdecillo), Sturnus sp. (Estornino), Tringa ochropus (Andarríos grande), Turdus viscivorus (Zorzal charlo) y Vanellus vanellus (Avefría europea). Los hábitats visitados se clasifican en comundidades fitocenológicas sencillas, explicando el autor la vida que debería hallarse en cada comunidad. También se incluyen algunos dibujos de aves a rotulador.
Field trip to Laguna de Duero (Valladolid) during the morning of the 22nd of February of 1952, of which there were observed the high activity of the Vole (Microtus sp.), the absence of frogs (without specifying species) and there were noted observations about the following birds: Acrocephalus arundinaceus (Great Reed-warbler), Alauda arvensis (Eurasian Skylark), Anas crecca (Common Teal), Anas penelope (Eurasian Wigeon), Anas platyrhynchos (Mallard), Ardea cinerea (Grey Heron), Carduelis carduelis (European Goldfinch), Carduelis chloris (European Greenfinch), Clamator glandarius (Great Spotted Cuckoo), Columba palumbus (Common Wood-pigeon), Corvus corone (Carrion Crow), Corvus frugilegus (Rook), Corvus monedula (Eurasian Jackdaw, refered as Coloeus by the author), Dendrocopos sp. (Woodpecker, refered as Dryobates sp. by the author), Emberiza cia (Rock Bunting), Emberiza cirlus (Cirl Bunting), Emberiza schoeniclus (Reed Bunting), Fringilla sp. (Chaffinch), Gallinago gallinago (Common Snipe, refered as Capella gallinago by the author), Gallinula chloropus (Common Moorhen), Larus ridibundus (Common Black-headed Gull), Limosa limosa (Black-tailed Godwit), Lophophanes cristatus (Crested Tit, refered as Parus cristatus by the author), Lullula arborea (Wood Lark), Lymnocryptes minimus (Jack Snipe), Miliaria calandra (Corn Bunting, refered as Emberiza calandra by the author), Motacilla alba (White Wagtail), Motacilla cinerea (Grey Wagtail), Motacilla sp. (Wagtail), Parus major (Great Tit), Passer montanus (Eurasian Tree Sparrow), Periparus ater (Coal Tit, refered as Parus ater by the author), Pica pica (Black-billed Magpie), Picus viridis (Eurasian Green Woodpecker), Podiceps sp. (that may be P.cristatus, P.nigricollis or Tachybaptus ruficollis), Regulus sp. (Kinglet), Saxicola torquata (African Stonechat), Serinus serinus (European Serin), Sturnus sp. (Starling), Tringa ochropus (Green Sandpiper), Turdus viscivorus (Mistle Thrush) and Vanellus vanellus (Northern Lapwing). Habitats were clasified in phitocenological communities, referring the author what organisms may be expected at each community. Some felt-tip pen illustrations of birds are also included.
