Owls And Kestrels

A nest box with camera is a great way of monitoring birds so as not to disturb the family unnecessarily until the time comes to ring the youngsters. The images of 31 May and then 8 June from Jamie’s camera documented the Kestrel’s progress so well that we were able to set the date for ringing the chicks as Monday 13 June. I met Andy on site at 1000 where we borrowed Steve’s ladder to investigate. 

Kestrels - 31 May

Kestrels - 8 June

We expected to find three chicks but were happy no see four young and feisty Kestrels at an ideal stage to accept their new rings. 

 

Kestrel

Kestrels - 13 June 

Ten minutes after ringing both adult Kestrels returned with animal food for the chicks. The same site has breeding Barn Owls and Kestrels together with Little Owls nearby, a variety of predators that points to a healthy population of voles, mice, rats and small birds in the adjacent and sympathetically farmed land. 

You can follow the progress of this Kestrel family on Jamie’s live nest box streams at https://www.facebook.com/NestBoxLive. There are birds from all over the world including Tree Sparrows, Swifts, Bluebirds plus owls and raptors alike. Be warned, the site is very addictive! 

Our visit was also timed to check the Barn Owl box that had not sent images for weeks. Andy climbed the ladder because he’s the youngest but not by much. He reported the camera lens buried in debris from many meals and their aftermath and advised the camera be cleaned and placed higher once the owls had finished. Of the four young Barn Owls just three were big enough to ring. 

Barn Owl Box

 

Barn Owl

 

Barn Owls lay 4-6 eggs but not all eggs hatch though 4 is the average as some may be infertile. Most bird species don’t start to incubate (sit on and warm) their eggs until the clutch is complete, so the eggs hatch at more or less the same time. 

Barn Owls begin incubation as soon as the first egg is laid and lay additional eggs over a period of around 8-21 days. After 31-32 days’ incubation, the eggs hatch every 2-3 days, usually in the order they were laid. This is known as “asynchronous” hatching. The age difference between the oldest and youngest nestlings can be as much as three weeks. This age variation serves to reduce the peak in food demand and spread it over a longer period. 

Today’s smallest chick will remain un-ringed because if we were to return to ring that one there is a real risk that its larger siblings might leave the box prematurely and thus be in danger in an outside world that they are not quite ready to enter. 

Back home three young Dunnocks (from 5 eggs) were old enough to be ringed and their details recorded on the BTO database, each with their personal ring number, the place of birth, their approximate age and the number of siblings in the family. 

Dunnock chicks

 

Back soon with more birds, news and pictures on Another Bird Blog. 

Boxing News

A few weeks ago I mentioned how Andy’s contacts had invited him along to see progress in two nest boxes installed at their home. At that time a pair of Kestrels occupied a box located on a building and a pair of Barn Owls occupied a box not too far away in an open fronted barn. By using a nest box camera it was possible to see that the Kestrels had laid 5 eggs and the owls had 8 eggs. 

Barn Owl

Armed with our Barn Owl Schedule One Licence and ringing gear we went along on Monday in the hope of catching the youngsters at an appropriate age to fit their rings. Our general ringing licence covers the ringing of Kestrels but extra protection afforded to Barn Owls requires stricter rules.

Andy went up to the Barn Owl box and brought down 3 chicks. One small one proved too tiny for a “G” ring while the other two were about right, each with well-developed legs and feet. 

Barn Owl Box

Barn Owl - too small for a ring 

Barn Owl

Barn Owls begin incubation as soon as the first egg is laid and lay additional eggs over a period of around 8-21 days. After 31-32 days' incubation the eggs hatch every 2-3 days, usually in the order they were laid. This is termed “asynchronous” hatching. The age difference between the oldest and youngest nestling can be as much as three weeks. This age variation reduces the peak in food demand and spreads it over a longer period. The female does all the incubation and the male provides all the food until the young are around 3 weeks old. 

Research shows that Barn Owls regularly let their nest mates know whether they plan to compete for an incoming meal or not. The delivery of usually a rodent of some sort is fed only to a single offspring at a time, chicks queue up based on their hunger level. This approach prevents arguments (in the form of beak stabbing and stealing) from breaking out when the food arrives, thus ensuring the maximum survival of the brood. 

It will be several more weeks before our two young owls are old enough to leave the box and fend for themselves. Meanwhile the camera should let us know how they all develop, including the runt. 

Meanwhile, four juvenile Kestrels were of an ideal size and age to take an “E” ring. From their size we estimated they should fledge in about a week or ten days. 

Kestrel  

Kestrel 

We also took advantage of a brood of five Barn Swallows that were at the ideal age for ringing. 

Swallow 

Swallow nest

All in all, a successful and productive few hours.

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Linking today with Anni's Birding and World Bird Wednesday.

Interesting

A few interesting recoveries of ringed birds came through; information on what happened to one of the four Kestrel chicks Will and I ringed at Out Rawcliffe in June last year, a further capture of a Goldfinch Will ringed in his garden in April 2010, and thirdly, interesting Chaffinch data.

Kestrel chick June 2010
Out Rawcliffe to Hathersage

We ringed four Kestrel chicks from a tree cavity nest on 20 June 2010, and one of these birds was found dead near Hathersage, Derbyshire on 17 December 2010. The first thing that springs to mind is that mid-December was a period of very cold, icy and snowy weather when perhaps an inexperienced bird might struggle to find food. Of course Kestrels with their habit of feeding and hovering along road and motorway verges are also likely to become road casualties. We have no further details of how and where Kestrel EK91584 was found other than it was freshly dead but I think my money would be on winter starvation.

Kestrel

The second recovery continued recent results from our Goldfinch ringing that shows movements of our local Goldfinches to and from the south of England. In the latest case, Goldfinch X515556 that Will ringed in his garden on April 25th 2010 was recaptured by another ringer in the south west of England in Broad Oak, Devon on 28 December 2010, clearly a case of a Goldfinch moving south during the winter. Of course unlike the Kestrel, the Goldfinch remains in circulation and as a species caught in good number may provide further information.

Garstang to Devon
Goldfinch

A third recovery more interesting from a longevity perspective was a Chaffinch first ringed near Lancaster on December 2nd 2004 by a local ringer. The bird was recaptured in Will’s garden on 15 December 2010, some 2204 days, just over 6 years later. The distance between the two ringing sites is 28 km only, showing that this particular bird is probably very much a resident of the local area and doesn’t venture far even in the winter.

Chaffinch