This dataset contains data from: Krist, M. (2004) Importance of competition for food and nest-sites in aggressive behaviour of Collared Flycatcher Ficedula albicollis. Bird Study, 51, 41-47. Data collector: Miloš Krist, e-mail: milos.krist@upol.cz Dataset is saved as CSV file separated by semicolons. There are no special symbols for missing data. Missing data are simply empty cells in the spreadsheed. The dataset has following columns: 1) Species - intruder species exposed in this trial. 2) Sex - sex of the defending parent. If both male and female were present during the trial, reactions of each of them are given on separate rows of the table. 3) Distance - binary variable describing whether the dummy was exposed directly on the roof of the nest box (=nest-box) or in the distance of two meters from the nest-box (=two meters). 4) Breeding stage - breeding stage when trial was done. 5) Nest - nest identity. 6) Date of the trial - in format YYYY-MM-DD. 7) Contact? - whether the parent contacted the dummy (=1) or not (=0). 8) Number of hovers - number of hovering flies done against the dummy during the 10-min observational interval. 9) Latency hovers - latency from arrival of the parent to the first hover against the dummy (in seconds). If no hover was done, latency was stated as 600s. 10) PC1 hovers - first principal component from the number of hovers and latency to the first hover. 11) Number of dives - number of dive attacks done against the dummy during the 10-min observational interval. 12) Latency hovers - latency from arrival of the parent to the first dive attack against the dummy (in seconds). If no dive attack was done, the latency was stated as 600s. 13) PC1 dives - first principal component from the number of dive attacks and latency to the first dive attack. 14) Latency nest-box - latency from parental arrival to its enter into the nest-box. 15) Offspring age - age in days, hatch day=0. 16) Clutch/brood size - at the time of trial. 17) Laying date - relative laying date. The day of the first egg laid in the population in particular year=0. For example, day 10 in the first row of the table means that egg laying in this nest began 10 days after the first egg was laid in the population in 1998. 18) Breeding success - number of fledged chicks/clutch size*100.