Limosa 94 (4) 2021 Estimating the number of terns visiting a breeding colony of Sandwich Terns Thalasseus sandvicensis on Texel, the Netherlands  (SPAANS B, LEOPOLD M & LOOS B)  Counting nests of Purple Herons Ardea purpurea using drones (VAN DER KOOIJ H)  Mixed breeding of a male Red-backed Shrike Lanius collurio and a female Woodchat Shrike L. senator in the Netherlands (FEENSTRA M, UBELS B & GEERTSMA M)  Are the timing of arrival and departure of Barn Swallow Hirundo rustica in the Netherlands correlated? (LENSINK R & PILZECKER J)  Arrival of Great Egrets Ardea alba on roosts: difference between adults and juveniles (LENSINK R)  Song Thrush Turdus philomelos eating a Common Frog Rana temporaria (BRINKMAN C)  Andermans Veren (KLEEFSTRA R)