Since the last article was written, we've completed our last week of tracking and presented our findings at Members' Night. We can happily report that we have had no new fatalities that we

King (A05) photographed in Witcham Plantation

know of, although one owl of which we were quite fond, King, is currently missing in action. King was our only male owl, and was probably the most adventurous of the bunch. He flitted constantly between Amport and Furzedown, and more recently has spent a lot of time at Witcham Plantation. This is a mainly young plantation consisting primarily of cherry and ash trees, and so we were somewhat surprised at his choice of roost site. But in some respects we were quite pleased as it was very easy to track him at this site, and there was always a good chance we'd get a glimpse of him.

But on the 26^th of August his signal disappeared, and has not been found since. We had a fairly good scout around the local area, with no success. This indicates that King has dispersed to pastures new, or that his transmitter has failed. We also had temporary fears for Packham (A09), who was a (usually) reliable fixture in Furzedown wood, as her signal vanished for a couple of days in the last week, but was rediscovered back in Furzedown on the 30^th August. Lorenz (A06) surprised us by roosting outside of Gollard Copse for the first time. For a couple of days all we could get was a faint signal towards Great Vinnels Copse to the south, but could not investigate further as we needed to obtain permission from the landowner. Once this was sorted out, we did manage to track down the owl to Great Vinnels. This was the last known location of Lorenz. The other owls, Audubon (A02), Goodall (A03), Darwin (A04) and Saba (A07) have all remained more or less in the same areas they were at the time of writing the last article, and we have been very lucky to sight them on several occasions and obtain more photos.

Saba (A07) photographed near Bush Farm

Unfortunately we have no more news on Attenborough (A08) and Durrell (A10) as their signals have not re-emerged. We suspect that these owls are still alive, only lacking a working transmitter. It's possible that they have succumbed to water damage, as the wire connections on the backs of the tags were not waterproofed. Alternatively, the owls have actually dispersed but simply have elusive signals as a result of their locations. We have discovered during the course of tracking that some signals just cannot be picked up until we're almost on top of them, so perhaps we have been looking for Attenborough and Durrell in the wrong places.

We've made a number of behavioural observations throughout the study. Firstly, it was clear that the owls seemed to prefer the edges of woodlands and the open rides through the woods, as well as strips of woodland that act as wildlife corridors. Maybe this preference derives from the need to have easy access to open hunting grounds where prey species such as rodents are abundant. It was also clear that some owls were much more adventurous than others. For example Saba (A07) was always on the move, whereas Darwin (A04) spent almost the whole duration of the study in a hedgerow at Amport woods. Additionally, we have been surprised at how often we've seen our owls roosting very low in trees with sparse cover. The reason for this is not clear.

We have attempted some basic analysis of our results, although at this stage we are limited as to what we can do due to the small sample size. Probably our clearest result is a strong pattern concerning the distances moved between roost sites from night to night. Figure 1 shows that when all the movements for the owls are totted up, the frequency of smaller distances moved is much higher than that of longer distances. So, the owls are most likely to move less than 100m between roost sites, and not very likely to move as far as 1km. There could be many possible explanations for this behaviour, for example the birds may be trying to minimize energy expenditure, especially if they are satisfied with their current location. Also they may try to avoid crossing large areas of open land where they will be more easily seen by both predators and prey.

Figure 1: Bar Graph Showing the Distances Moved Between Roost Sites

We think that in future it may be useful to look for correlations between factors such as body weight at release and distance moved, and between size of foster aviary while at the Park and distance moved.

Recommendations for future years include carrying out surveys of small mammal populations in each of the release sites, as well as finding out what species of predators are present, and in what densities. These types of factors can have a strong bearing on the survival of released tawny owls. Also we would suggest having a larger sample size if finances can stretch to it, and ideally equal sex ratios to allow for behavioural comparisons to be made between males and females. Finally we would recommend changing one variable every year to determine what effect this has on the owls' success, such as providing hack sites or using different release locations.

The girls just before their presentation on Member's Night

Saturday night was our last as official tawny owl researchers, and we shared our experience with the Members' Night crowd via a forty-minute presentation. Despite our nerves, we were able to present our findings without any major hitches, and received plenty of encouragement and support from everyone there. We're all sad to be leaving, but hopefully we have not heard the last of our owls, as they will still be monitored in the months to come. Autumn will be the critical time for our owls, as it is now essential that they establish a territory. Failure to do so could result in long-distance dispersal or death. Nevertheless, we have a lot of confidence in them, as they have obviously been able to learn to fend for themselves, and when we've seen them they've generally been looking fit and strong.