Busy day monitoring Tawny owls

On Tuesday I visited the Tawny owl boxes I monitor on behalf of the Gloucestershire raptor monitoring group. Last year myself and Rich Harris from the group built and erected 82 Tawny owl boxes as part of a new scheme to monitor the species in two areas of Gloucestershire, Rich took the lions share of boxes partly because he has more time on his hands and was doing a great job at contacting landowners and also because the area I'm monitoring tie's in with veteran Tawny owl man Steve Palmer who has approximately 80 boxes of his own. I visited the 25 boxes yesterday as a preliminary check to gauge the occupation and status of the boxes.25 boxes might not seem like a lot but in one day that's plenty to try and get round, some of the boxes were to replace old boxes and were in areas where I had monitored Tawny owls before but many were in new sites. Tawny owls are easily our most common owl in Britain, the classic call that people associate with all owls is that of the Tawny owl usually at its peak during mid winter as pairs begin to reclaim territories and single birds try to win a territory. I try and get round any potential sites before putting a box up to see which areas have the most vocal activity, recent BTO records have shown a fall in reports of Tawny owls in certain areas and as studying owls can be quite a anti social activity due to their nocturnal habits I was keen to start looking into their lives and tie in with Steve Palmer's long standing study of the species. Putting a box up where a bird is calling doesn't guarantee success but its a good place to start. Tawny owls will nest in holes in trees, old nests, tops of old squirrel drey's and have even been known to nest on the ground.

Tawny owl box in location

It is widely  acknowledged by people monitoring this species that Tawny owls are susceptible to disturbance and desertion of eggs in the very early stages of laying or prospecting for a nest and because they are early breeders I try and stall my check's to Late March. I was a bit late this year due to busy Easter holidays but that didn't matter to much, in my opinion in order to get a proper gauge on how this current year is going to be for Tawny owl I like to find out how many egg's the female has laid, this can give us clue's to individual birds as we know that young or new pairs will sometimes only lay 1 or 2 eggs whereas an older breeding bird may lay up to 4. The amount of eggs laid also proves that the male must be successful providing food in order to get the female into breeding condition and if she is in good condition then she will potentially be able to lay more eggs. When it comes to the egg's hatching the shell's will soon be broken down and even eaten by the female, if I go and check the box and find one or two chicks and I've done an egg count previously of 3 I know something has either happened to the egg if its not there or a chick has hatched and died possibly or sometimes an egg may not hatch. If I left it to mid April to do my checks and ring chicks, I may find only one chick or nothing when possibly 3 have hatched, this could be due to the death of a parent bird or a lack of food being brought into the box among other factors so again I can get a better picture of what is happening with these specific checks. We also know Tawny owl chicks will branch at around 3 weeks old so checking egg's and small chicks help's me gauge when this might happen and hopefully I don't miss anything, of course you could always go listening for chick's food begging during April. Other thing's I can gather is whether it is the same female in that territory if the incubating bird is wearing a ring, last year I caught a female that was 11 years old and had only travelled 1km from her natal site, this year I caught a female who is 7 years old and had only crossed a road to breed in this woodland. To me this is fascinating and important data that helps safe guard the future of this species and many others, we can also over a longer period of time look into the laying and hatching dates of the species in the area and correlate this to things like climate change.  The welfare of the birds is paramount during these checks and myself and Steve Palmer with 30 + years of monitoring Tawny owls are yet to find a pair that we have checked and had desert a clutch of eggs or young due to our interference.

Clutch of two Tawny owl egg's - All owl egg's are white and is thought to be partly that they don't need camouflage like other species eggs 

The 25 boxes I checked I am pleased to say had a very good up take, from those 25 boxes 8 had breeding Tawny owls in them and one had a roosting bird within it, two of the adult females had rings on, one I had met last year and a new one but both from Steve Palmer's nest boxes nearby. The 6 other adult females I put a ring on myself so they could turn up in the future and we will know a bit more about them, one of the advantages of monitoring owls in nest boxes is you can gather this sort of data easily. I can also check the condition of the birds by weight, feeling their keel bone and looking at their feather condition, all were in great condition. The other advantage with checking the boxes is I can see at what food is being brought in and how much. Owls like other birds of prey will cache food and if the male has a successful evening hunting he will deposit a lot of the food in the box, it makes perfect sense if you don't know what's around the corner and you have a family to feed. This year the boxes were full of wood mice, baby rat's, small passerine feathers and one even had half a Jackdaw in it, Tawny owls are pretty ferocious birds!! Check out the image below for a fine example of how important birds of prey and owls are as natural pest control and why you shouldn't put rat poison down!!

Three Tawny owl chicks surrounded by no less than 5 baby Brown rats

On the topic of ferocious Tawny owls some people may have heard that Tawny owls can be extremely protective over nest sites and those of an older generation may know the story of famous wildlife photographer Eric Hosking who lost an eye to a protective Tawny owl around the nest site. When I am carrying out any check on cavity species I am always careful, I've had squirrels scare me on many occasions jumping out of a box as I climb the ladder but at this stage Tawny owls don't tend to be as aggressive, I have only had the misfortune of being hit by a Tawny owl once before, it hurt but it tends to be when the chicks are bigger and the female isn't brooding them but is sat nearby watching the nest site. Never the less precaution should be taken at all times so steer clear of Tawny nest sites unless experienced in checking them. When we have done the checks, gathered the data and checked the female we gently place her back in the box, this is very straight forward and we then retreat quietly and quickly and allow her to carry on raising her young or incubating eggs.

Natalie from the GRMG with adult Tawny owl - We must stress all of this is done under licence with years of experience

As mentioned above all of this is carried out under licence from the BTO by experienced and trained field workers, the welfare of the birds is of complete paramount and the information and data received is fed back to the BTO and other organisations. This date really is what produces the ammunition to protect these species and where they live, Raptor Aid is very proud to working on real conservation initiatives. In the next 2-3 weeks we will go back to check on the progress of these chicks so we will keep you posted on their progress with a possible video in the making. If you have any questions or queries please feel free to get in touch.

Thanks for reading!

Jimmi