So far, I have identified and named 29 individual birds. I have summarized my findings in two sets of maps, one map for each of the 17 visits, and one for each named bird.

From the end of March till the middle of April, song activity was very low. Song activity peaked from June onwards, with many new birds appearing, which may be young born the same year. Early in the season, it seemed as if most songtypes were unique to a single individual, but later in the year I found many birds sharing songtypes. In part, this may just be because my collection of recorded birds grew, but one also get the impression that late in the season, a lot of birds started to copy songtypes from their neighbors, which may be young birds learning to sing by copying their neighbors.

Many named individuals did all their singing in a very small area, sometimes less than 100 meters across, but others had songposts up to 300 meters apart. Some birds apparently moved during the season. Many birds were only recorded during a few visits. Sometimes, these visits are evenly spread over the season, but sometimes they are clustered. Some birds fell silent during a long time and then reappeared. This may mean that these birds moved in and out of my study area which is approximately 1 km across, but it may also be that some birds fall silent when they have to care for a brood, which may explain why there was very little song activity at the end of March and in early April. Two birds (Bert and Vaclav) used the same small area of about 100 meters across. I observed two male Yellowhammers on this location during many visits, but it took quite long before I finally heard the second one singing.

A somewhat detailed observation I made was that some birds like Wim sing the endphrase differently depending on the songtype they use for the opening phrase. The endphrase can sometimes also give useful information for individual recognition since two birds may use the same songtype, but differ slightly in how they sing the endphrase in aspects like its relative height compared to the opening phrase, whether it is completely flat or rising at the beginning, or how wide it is. It was my impression that one bird (Karel) changed his dialect during the season. However, I am no longer sure that what seemed like the second syllable of the endphrase in one recording from April 15 is really made by him. In some birds, there seems to be development in time in how they sing a certain songtype. A good example of this is Arie, who changed his way of singing the songtype A.

Individual recognition of Yellowhammers is time consuming. In fact, analyzing the results takes far more time than collecting the data, although I hope this will improve in the coming years as my experience grows and I can use the set-up created during the first year. In view of the amount of time needed, individual recognition of Yellowhammers by their sound is probably not a practical way of counting Yellowhammers. In the end, however, it gives considerably more information. In 2012, I tried to count yellowhammers in a part of my study area by more conventional methods and estimated the number of territories there at 7-8. In 2016, I recorded 11 different birds in this area while 2 more birds visited it and sang there at least once. Apart from this, the method of individual recognition gives much more information such as about movement of birds. Unfortunately, my study area is still relatively small so that some birds may have moved in and out of it during the season. It seems likely that some birds that have been recorded only once or twice moved around a lot and only visited my study area for a short time. However, some birds also seem to be present during the whole season but to sing very little.

If I count all named birds as territories I arrive at a density of 40 pairs / square km, but this is probably an overestimate given that some birds probably stayed only a short time in the study area and others had territories that overlap only partly with the study area. Also, birds breeding in the study area may forage on the surrounding fields which are unsuitable for breeding. Nevertheless, the density of yellowhammers in the study area seems to be very high.