The Nest Box Diary 2011

August (part 3)

- The final week? 

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20 August - A day of bright sunshine interrupted by a period of rain, sometimes heavy in the middle of the day. The temperature at 7am was 14C, rising to 19C by noon, by which time the clouds had moved in for the south-west and the rain had started. The temperature then dropped a couple of degrees. However, by 3pm the tail end of the cloud bank moved away to the north-east, leaving clear skies over us, and by the end of the afternoon a high of 21C had been reached.

The Swifts' behaviour reflected the weather pattern. The adults left together at 5.40am and during the morning returned 10 times. With the arrival of the rain there was then a gap for over three hours between the pair leaving the box at 11.31am and one of them returning at 3.25pm. During the rest of the day the parents returned to the box 15 times to give a total of 25 returns by the time they retired for the night at 8.34/8.38pm.




21 August - A bright start, with a temperature of 15C at 7am, and 20C by noon before high cloud arrived accompanied by a few drops of rain. This dissipated fairly quickly with no effect on the frequency of visits today. During the afternoon the temperature rose slowly until a high of 23C was reached around 6pm after which it began clouding over again.

It turned out to be a record day for the parents in SW-ri with them returning to the box a total of 23 times after leaving together to start the day at 5.45am. By noon the parents had returned 13 times. a further 12 visits followed in the afternoon, with the evening seeing the final 7 visits. They returned together for the night at 8.35pm, just as the red sky in the west was fading.

Swift chick looking out this evening, 21 August, 2011


The chicks were almost out of the nest cup as much as in it today, one of them especially, with one spending prolonged sessions looking out.

This picture was taken this evening while the chicks were left alone for the longest period all day (7.14pm to 8.18pm).




Swift chicks - wing excercises, 21 August, 2011

With just a week to go the wing exercises are taking place more frequently and this still from the video feed  indicates just how long the chicks' wings are now.

It appears that the wingspan of this chick is just about equal to the internal length of the box which has a floor area of 27 x 17cm.





22 August - A bright and mainly sunny day with the temperature at 7am being 10C but rising to 22C by 3pm in a light breeze that started from the north-east but which swung to the east south-east late in the day.

For the Swifts it was a pretty 'normal' day after a slightly slow, staggered start. The adults left at 6.06/7.02am before returning to the box 23 times by the time they retired for the night. Eleven of those visits took place before noon. During the afternoon there were longer gaps (of up to an hour) between visits and with just two exceptions in the early afternoon, when they did visit both parents turned up. In the evening the chicks were left alone for just under two hours before their parents finally returned at 8.20/8.22pm.





23 August - What a contrast to yesterday - heavily overcast skies all day with almost constant mist and/or drizzle. A temperature of 15C at 7am wasn't improved on all day.

The Swifts' reaction to the weather was to stay put until 10.25am. Once the parents finally headed out they returned to the nest just 10 times today, six of these visits  occurring after 6pm when the drizzle had all but stopped (but with no let-up of the low cloud).





24 August - A much better day, although Swift activity remained somewhat restricted.

Early rain and mist had largely cleared by 9am and the day became brighter as the morning progressed. The temperature of 14C at 7am wasn't improved upon until after 9am and then rose slowly until it reached a high of 20C in mid-afternoon. It had dropped back to 15C by 8pm.

The parents left the nest box at 7.41am and despite the improving conditions they didn't return until the very end of the morning, when they arrived together at 11.54am. During the rest of the day they returned a further 13 times, which is about the number of visits I would have expected in the second half of the day.

I wonder why they stayed away during the morning. Perhaps it's a sign that we are getting close to the 'fledging window' now, although if my calculations are correct the chicks' departure is still at least three days away.





25 August - Another wet start with heavily overcast skies and quite heavy rain at 8.30am, although the forecast is for sunshine by 10am - fingers crossed!

By the time we headed out at 10am to take one of our grand-children to a music session at the local library there was a small patch of milky blue sky to the west. When we left the library an hour later coats were no longer needed. The rest of the day was bright, with sunshine and puffy clouds, although this evening there is a layer of high cloud which is probably a sign of the heavy rain forecast for overnight and into tomorrow.


As usual, the adult Swifts' behaviour reflected the weather pattern in that they didn't leave the box until 10.27am, not having approached the exit until just a few minutes beforehand. Once out they returned to the chicks nine times before the end of the afternoon (6pm), followed by ten more returns in the evening, seven of which took place after 8pm. Both adults were in the box by 8.17pm, although one left again to return for the final time at 8.20pm.



With the prospect of heading off to Africa ahead of them within the next few days, the chicks looked out quite a bit today, and there were three quite vigorous wing stretching sessions seen during the day.

Swift chick stretches across diagonal of box, 25 August 2011On this occasion, one chick took a break from looking out to stretch, using the full length of the box. It appears to have a wingspan that is now longer than the diagonal across the floor of the box (which is 32cm). I estimate that its wingspan may be around 34cm, still short of the adult wingspan of 40-44cm, but certainly longer than seen in the image of the 21st.

An adult Swift is 17 - 18.5cm long. Coincidentally, the box measures 17cm front to back. This chick appears to be just short of that measurement.





26 August - The weather continues to ensure less than ideal insect hunting conditions for the adult Swifts.

Low cloud and heavy drizzle at the start of the day continued until around 10am before the cloud broke up somewhat to provide brighter conditions with some sunshine and numerous showers through the rest of the day. The temperature was 13C at 7am and a high of 17C was achieved for a couple of hours in mid-afternoon. The day started off with a northerly breeze, but this soon swung to the west where it stayed for the rest of the day. By 8pm the sky was almost cloudless and the temperature was back down to 13C.

This morning the adults didn't wait for the rain to end before they left the box at 8.58/9.03am, although it was 11.43am before one of them returned to the box for the first time. There was just one more visit (at 11.55am) before noon. Between then and 6pm there were four more food deliveries.

This evening there were nine more returns by the adults, including one time when both parents arrived together (for the first time today) at 8.15pm. They finally retired for the night at 8.24/8.27pm.


Swift chicks climbs onto ledge over box entrance, 26 August 2011Once again the chicks shared their time between looking out, exercising their flight muscles, but with most time spent resting in the nest cup. One event was reminiscent of the chicks in SW-le just a day or so before they fledged  in that one of the chicks climbed up onto the triangular 'canopy' over the exit.

It seemed to take advantage of this elevated position to bend its tail downwards as it stretched its wings.



A Swift chick exercises its tail muscles, 26 August 2011


A bit later and it was forcing its tail upwards, an exercise that it repeated several times,




A Swift chick exercises its tail muscles (2), 26 August 2011



before twisting it to the side. These are all movements that will be essential to the young bird's manoeuvrability once it takes to the air in the very near future.




One thing is noticeable about this brood - there are few of the characteristic Swift screams to be heard. In fact the most frequent sounds heard are those 'sub-songs(?) that I commented on previously. However, the chicks are now generating another sound, not vocal this time but generated by the rapid vibration of their wings as they beg for more food after a parent has already given up its bolus of insects.

Click here to listen to a sequence recorded at around 8.23pm after one of the adults brought in food and fed one of the chicks. The sequence lasts 45 seconds and has a file size of 656KB. That adult was resting before leaving again and as both chicks were making almost continuous but very quiet chirping sounds, one of the chicks (I can't tell which chick had just been fed) was vibrating the shoulder region of its wings.

I was standing in our driveway during the visit and during the whole event the only sound I heard was that of the adult brushing against the wood on entering and leaving the box. Is the almost complete lack of the characteristic screams down to the absence of other Swifts, leaving no need to broadcast the family's presence, or is it defensive, to hide their presence in the absence of the mutual protection of other colony members?


Click on images to see larger versions


2011 Nestbox Diary Index .......... .......................................... August (part 4) & Sept