June 24, 2015 MCSI Update ~ The Major Upside and Lowdown Report: twig collections, new site discoveries, and incubation is underway!
Since our last update, for the fifth and final formal 2015 monitoring session (MCSI Blitz Night June 6 – alternate date of June 5), your efforts have led to some remarkable observations and new site discoveries. Your data have shown that roosting chimney swifts appear to be redistributing themselves from some spring roosts. At nest sites, chimney swifts have laid eggs and are incubating them now ~ a monitoring primer will follow, using the St. Adolphe flock as a template for what you may see elsewhere in the province.
Ashley had golden moments in St. Vital. On June 19, a chimney swift “landed” on a huge oak tree in her front yard for about 5 seconds. After take off, the swift circled and repeated the short-lived “touch and go” landing while a second swift circled about and chittered. On Father’s Day (June 21), the same behavior took place between 5-6 PM. Ashley was ready for a closer look: the chimney swifts “were branch bouncing, and going for the tips of the branches. What a sight to see!” The swifts were collecting twigs for nest building. Now the challenge is on to find the nearby nest site!
Paul and Valorie travelled to Darlingford and have put that community on the chimney swift map – congratulations on documenting the entries of 2 swifts into the Darlingford School Heritage Museum on June 18! This is the ninth new site identified for 2015.
The news of three more new site discoveries, for our MCSI database, arrived after a flock of observers spread out in Melita on June 22! I am sorry the names of all the observers have not winged their way in yet – we hope to thank you all in person soon. The new Melita sites are:
2015-10: Antler River Historical Society; 3 swifts entered
2015-11: Legion Memorial Hall; 3 swifts entered
2015-12: Melita and Area Health Centre; 2 swifts entered
Moving on to roost sites, we mentioned previously that the Dauphin peak seems to have occurred around June 1 with ~30 swifts, as on June 6 only 15 swifts roosted for the night. In Winnipeg, it took a week longer for numbers to peak and decline at the Assiniboine School; ~166 roosted on June 6 (~122 roosted on June 1) whereas ~80 swifts roosted on June 14 and June 17.
In review (from the June 8 BlogSpot featuring Dave Lavigne’s photo of a swift carrying a twig), during the nest building stage, a breeding pair of chimney swifts will collect 8-12 twigs per day. Using sticky salivary gland secretions, the twigs are attached to the rough interior of a nest site to form a cup shaped nest. After a week, the female starts to lay eggs (Kyle and Kyle, 2005). However, the nest cup is considerably undersized at this point so the pair continues to bring in nesting material through the incubation period (Kyle and Kyle, 2005). Nest building in Manitoba begins shortly after the spring migrants arrive. So, there is between year variation in the date of onset, but nest building typically starts around May 22 (range is May 10 for early arrivals to June 25 for late arriving pairs)(see Stewart and Stewart 2013 – http://www.mbchimneyswift.ca/Documents/2013_BlueJay.pdf ). The spring arrival of the swifts was delayed by poor weather in 2015 and your monitoring data showed nest building was off to a slow start. During nest building, you will not always see the breeding pair travel together; they may enter or exit the site individually. The duration in the chimney and the between-visit interval varies considerably at 1 to 70 min and from 1 to 50 min, respectively (see Stewart and Stewart, 2010 – http://www.mbchimneyswift.ca/Documents/bluejay2010.pdf ).
On to egg laying and incubation: the Kyle’s work in Texas has shown that mating occurs inside the chimney and copulation occurs daily. Eggs are laid every second day and incubation starts with the second last egg; the clutch size varies between 2-7. Both adults share incubation duties which last 18-21 days.
In St. Adolphe, we noted clutch sizes ranging from 3 to 7 eggs. For nesting attempts between 2007-2013, the median date when incubation started was June 26 (range from June 3 to July 16 for late arriving pairs = 43 day range).
Monitoring data can be tricky to interpret during the egg laying stage. During incubation, monitoring can be downright tedious when the swifts are “tight on their eggs”. Some recently collected data can be used to explain these concepts.
On Sunday, June 21, I savoured a solstice moment and watched the Club Amical chimneys between 11:15 AM and 12:55 PM (100 minutes). No entry/exit events were seen for the SE chimney. This is what happened in the NE chimney: entry at 11:34:21; exit at 11:52:33; entry at 12:24:10; entry at 12:32:04; exit at 12:32:43; exit at 12:43:16. For the first entry/exit sequence, the duration in the chimney was about 18 minutes. The time from the exit to the subsequent entry yielded a between-visit interval of ~32 minutes. The consecutive entries and exits toward the end of the observation period indicate that the pair were out of the chimney together and the nest site was unattended. Nest building was underway at this site on June 1, so egg laying might have started around June 10 and incubation of a large clutch of 7 would start by June 24. When I watched on June 21, the NE Club pair were likely transitioning from egg laying to incubation.
Classic incubation behaviour is seen when an entry is made and an exit follows quickly – within 30 seconds to 1 or 2 minutes; this typically occurs once per hour. Remember that the adults are sharing duties – the incoming partner takes over sitting on the eggs so the outgoing partner has a chance to forage. This explains the answer to a question I asked often in the early days – “why would a swift bother to come in to a chimney if it leaves so quickly?” – IT’S NOT THE SAME BIRD LEAVING. The “duration in” interval can be viewed as the “turnaround” time for partner exchange during incubation.
At the Church on Tuesday, June 23, I watched for 60 minutes between 6:40 PM and 7:40 PM. At 7:20:21 a swift entered; at 7:21:06 a swift exited the chimney. Nice – keep those eggs warm! But the tedious part is that you watch for an hour to see one entry and one exit separated by 44 seconds! Blink and you can miss all the action.
On Wednesday, June 24 in the early afternoon, I was fortunate to see another classic incubation exchange at the Main St. site; an entry took place then an exit occurred 46 seconds later. Then I shifted to watch the last site in town. The Brodeur Bros. pair left the site unattended for a 13 minute period; one swift then spent 38 minutes in the chimney before it was joined by it’s partner; one swift left the site 10 minutes later (exit, entry, entry, exit in 70 minutes of monitoring).
The bottom line for St. Adolphe this week = 4 of 5 nest sites are occupied; the breeding pairs at 2 sites (NE Club and Brodeur Bros.) are transitioning from egg laying to incubation; and the breeding pairs at 2 sites (Church and Main St.) are well established at the incubation stage.
For the days ahead: the transition from incubation to hatching is subtle – you typically will see two entry/exit cycles per hour as feeding brooded juveniles takes place; partners share brooding also, so the “entry to exit” time intervals are still for turnarounds. After 6-7 days, the youngsters can regulate their own body temperature and can be left unattended in the nest. So for feeding non-brooded juveniles (which occurs 3-4 times per hour in Manitoba), both adults may be out of the chimney – in which case the “entry to exit” intervals then return to single bird “duration in” scenarios. Fledging takes place with the first flight outside of the chimney, 28-30 days after hatching.
Confused? That is understandable. The world of nesting chimney swifts becomes simpler, after you spend some time looking at your data, while wrapping your head around what is actually going on inside the chimney. If you have any monitoring observations that need decoding, send them in as help is always available. The important thing is to ENJOY watching the chimney swifts. Document what you see and interpretation can follow.
We hope nest sites remain active through to fledging time in early August. The dynamics at roost sites will also change in August as the swifts prepare to migrate south. Until then, there is a lot of interesting chimney swift activity to experience. Your observations will be welcome!
Happy summer swifting, Barb.