JULY UPDATE: NEW BEGINNINGS
To our monitor’s credit, new sites are still being discovered and reported. Adding to our habitat inventory, and registering his second new site of the season, John reported the use of an old warehouse chimney at 579 McDermot (City Centre area of Winnipeg). John was monitoring for over 2 straight hours to document the July 3rd activity, “This morning I went back at 10:40 AM and had the first entry at 11:23 AM and exit at 11:28. Had to wait till 12:29 PM for the second entry and 12:48 for the exit.” With an entry/exit exchange once an hour, incubation is indicated at a nest site. Excellent work John!
John also had an interesting observation – “Crows were on and off the chimney many times as I watched. They appeared to look into the chimney but I saw no indication that they went in. Do you think they are a danger to the eggs or chicks?” Chimney Swift nests usually are 10-12′ (or lower) below the rim of a chimney. It would be difficult for a perching crow to reach ‘n’ grab a snack out of the bowl of the nest. Once big birds go into a chimney, either by choice or accident, they usually don’t get out (dead pigeons etc. have been seen in the cleanout traps of many chimneys) and there may be some collateral damage to swift nests on the way to the bottom. However, birds perching on the rim prevent swifts from using the chimney on their own schedule. I have seen pigeons and starlings sit on rims for up to 15 minutes and adult swifts have been put off entering – they veered off and repeated an approach. The drive to feed young is strong, so some swifts will eventually blitz past the intruder during a kamikaze entry. The reverse holds true also – adults may be pinned inside longer than they might normally stay and can blow past a bird on the rim with a meteoric exit. I have never seen a bird of prey sit on a rim, so that may be a game changer. Raccoons inside a chimney could dislodge nests and eat eggs or young juveniles. Pruning tree branches to prevent them from overhanging the chimney opening, and putting metal flashing or a collar around a chimney, helps to keep the pesky mammals out.
Ken, a member of our MCSI steering committee, has been out in Manitou recently. We have not had scouts in this town before. We will have details soon of Ken’s impressive sighting of Chimney Swifts using a site!
Now, other new beginnings start with the hatching of eggs…
There is always something new to learn or to remember that which has been forgotten. While it is useful to use standard date ranges and behaviour activity to identify stages of nesting, the transitions may not be crisp and distinct – that is the swifts may feather (sorry, bad pun intended) the progression between stages of nesting with “iffy” – “I wonder what they are doing now?” activity.
On Sunday and Monday (July 3 and 4 respectively), I arrived at the Church and NE Club Amical chimneys to discover feeding of hatchlings was underway! WAIT A MINUTE – I thought I was leading the big hatching events by a couple of days. Back to the datasheets: during some monitoring sessions, a few incubation exchanges were evident but unattended periods also were seen. The swifts were not “tight” on their eggs. It became apparent that by using the classic “one partner exchange per hour” rule, I underestimated the onset of incubation by 2 days. Fast forward to the home computer where I pulled up a species account for Chimney Swifts on the Cornell Lab of Ornithology site: https://www.allaboutbirds.org/guide/Chimney_Swift/lifehistory “Incubation period: 16-21 days.” That explained it. Do note the difference between the previously advertised, more widely accepted, range of 18-21 days.
Both pairs of swifts hatched out their eggs in just 16 days. What indicated the presence of hatchlings? It was an increase from the typical 1 entry/exit event per hour seen in incubation, to 2 entry/exit events per hour.
Take a look at the monitoring data for the Church, Sunday July 3, 1:19 – 2:24 PM:
- 1:27:20 entry
- 1:28:07 exit
- 1:56:00 entry
- 1:56:18 exit
- 2:20:30 entry
- 2:21:13 exit
There were intervals of ~28 and 24 minutes between visits (time from an exit to an entry), and very quick partner exchanges (time from an entry to an exit; this is also known as the “turnaround time” or “duration in” interval for single bird entry/exit sequences – more on that below).
Here is what happened at NE Club Amical, Monday July 4, 10:48 – 11:53 AM:
- 11:01:42 entry
- 11:02:06 exit
- 11:17:34 entry
- 11:19:03 exit
- 11:49:52 entry
- 11:50:15 exit
There were intervals of ~ 15 and 30 minutes between visits; partner exchanges took between ~30 – 90 seconds.
Once hatched, the juveniles cannot regulate their body temperature, so they are covered, or brooded, by an adult. This stage of feeding brooded young lasts 6 or 7 days (Day 1 of feeding = day of hatching).
When adults no longer brood their young, both adults can be out of the chimney foraging at the same time. At this stage of feeding non-brooded young, you will see consecutive entries or exits as the adults come and go – there is a lot of variability for the “between visit” and “duration in” intervals. Feeding rates may increase to 3-4 times per hour, or more, if a locally abundant insect patch is available.
At approximately Day 21-22, juveniles move out of the bowl of the nest and cling to the vertical wall. They start to practice flying up and down the shaft of the chimney to strengthen their flight muscles. The time soon comes to move beyond the confines of the nest site.
Fledging occurs at Day 28-30 and, for swifts, is defined as the first aerial excursion outside of the chimney. I have seen fledging delayed until Day 32 by persistent, high winds. During the first week after fledging, the juveniles will return to the nest site often to rest and be fed by their parents. Thereafter, flight proficiency, and independent feeding skills, develops quickly and the daytime use of the chimney ends.
Elsewhere in St Adolphe, the eggs in two more nests – SE Club Amical and Brodeur Bros. – are due to hatch within several days. I am tracking those sites closely now that I have been reminded of 16 day incubation periods!
A, presumably, young pair finally arrived mid-June at the Main St site. Last week, they seemed close to settling on eggs; incubation exchanges were seen. This week, the two were mostly out of the chimney, racing about town with the characteristic “V” wing position of pair bond displays. The pair may be staking territory out for next year more than trying to settle into a serious breeding attempt this year. Time will tell.
I will provide some monitoring updates to track the progress of the breeding St Adolphe Chimney Swifts during July. The roost site dynamics are important to follow too, so we’ll keep checking in on the non-breeding portion of our Manitoba Chimney Swifts.
Happy Swifting ’til next time, Barb.