“RULES OF FEATHER” FOR MONITORING CHIMNEY SWIFT NEST SITES.
IMPORTANT DATES, NUMBERS, AND THINGS TO EXPECT AS CHIMNEY SWIFTS ARRIVE, THEN TRANSITION TO NEST BUILDING.
Before launching into today’s blog, this is your friendly reminder that the 2022 MCSI program rolls out on Wednesday, May 25. We look forward to your reports of evening monitoring sessions at both roost and nest sites, and daytime monitoring of nest sites.
The 4-night National Roost Monitoring Program also starts up on May 25. MCSI supports this program by sharing our data with the national program organizers. We hope our contributions help improve the understanding of spring arrival and distribution dynamics of Chimney Swifts across Canada.
Amanda has sent out monitoring information – check the blog posted on May 3 (2022 Monitoring on the Horizon) for all the details. For an updated list of high priority sites that need status updates to confirm residency, check Amanda’s blog posted on May 18 (They Are Arriving! Chimney Swift Sightings and Priority Chimneys).
Many of you will be monitoring potential nest sites. The first 30 minutes of monitoring (in the 90-minute monitoring period) is actually considered “daytime” monitoring in the hopes that we may pick up some signs to determine if each site is being used for nesting or roosting (or both). Here are some general “Rules of Feather” to guide your journey of observation through the early stages of the breeding season…
ARRIVAL – around Mother’s Day, start looking for spring arriving Chimney Swifts.
The arrival stage is characterized by the first spring reports of Chimney Swifts. The birds may be identified by vocalizations or visual confirmation. You may hear the swift’s characteristic chittering or see small numbers of swifts foraging in the area of known roost or nest sites. Migrants are often first noted in many Manitoba communities on the same day.
Chimney Swifts will enter their sites, usually within ½ hour of sunset (½ hour before to ½ hour after sunset = the roosting hour), to rest for the night by clinging onto the rough interior walls. Sometimes roosting entries are made before the roosting hour and sometimes swifts are in the air and unaccounted for as total darkness descends.
Morning departures by roosting Chimney Swifts are thought to occur within ½ hour of sunrise (½ hour before to ½ hour after sunrise) in good weather conditions. Cold, rainy weather may delay morning egress.
The behaviour of Chimney Swifts must be interpreted in the context of what is going on in their environment. Chimney Swift behaviour doesn’t always follow textbook, black ‘n’ white rules. So, interpretation of behaviour is not always straightforward. We often see roosting entries before the official roosting hour during cold, rainy weather but those early roosting entries may also happen when local foraging seems very good and the weather is warm ‘n’ dry. We’d like to interview those swifts to explain themselves!
Not to be confused with breeding behaviour that involves daytime use of a chimney, Chimney Swifts may seek daytime refuge in their sites during inclement weather; this may be for short or long periods. I have seen Chimney Swifts enter the Church chimney in St Adolphe during intense thunder storms. Once the electricity finished after ~45 minutes, out popped the birds. From my notes made on May 30, 2017: “yesterday Tim saw ~70 CHSW enter Assiniboine School roost ~noon as he was onsite doing an outreach program… [today the weather is] clearing after 2 miserable cold (8-12 C) rainy BLEEP days with strong winds.” Those swifts likely hunkered down for several hours. Winnie Wake, our devoted colleague in London, ON, has noted similar daytime entries of Chimney Swifts at roost sites, which were associated with very poor weather. During times of refuge, Chimney Swifts have the capacity to enter a state of torpor which is a useful energy saving strategy.
NEST BUILDING – look for daytime entries and exits; Chimney Swifts will be at work in the morning, afternoon, and early evening.
In the latter half of May to early June, a breeding pair of Chimney Swifts will begin to gather small diameter twigs from the ends of dead tree branches. The twigs are taken into the chimney and glued together, with sticky saliva, to form a small cup-shaped nest. Approximately 1 week after nest construction begins, the structure is large enough to hold an egg. As eggs are being laid approximately every other day, nest building continues. Indeed, nest building will extend through to the end of incubation (more on that in the next blog). Once eggs hatch, adults focus their efforts on feeding their youngsters and nest building stops.
In St Adolphe, all successful breeding attempts had nest building underway by June 3-4. So, that is an important date for monitors to be aware of generally. Elsewhere in the province, successful nesting attempts may have had slightly later onsets of nest building, or perhaps a more protracted nest building phase. A Brandon site diligently monitored by Margaret & Millie had several late August fledging dates. Tim established the Provincial record last year as he tracked a breeding pair of swifts that took up residence in site 2021-T04, a newly constructed tower in the Selkirk Mental Health Centre. Nest building started just after the tower was constructed ~ June 18 and fledging took place ~ Sept. 9 (see blog Sept. 24, 2021 – Inside Story, Inside the Chimneys at St Adolphe, Assiniboine Park Zoo and Selkirk).
At your nest site, you may see a breeding pair approach the chimney together and drop in, one after the other. Or, the pair may approach together and as one bird drops in, the partner will veer off to circle and enter, or depart the area (to feed or gather nest material, etc.). Alternately, single birds may approach and enter the chimney. Chimney Swifts may fly low over the chimney vocalizing as they pass by. Single or two consecutive exits may follow after a time lag. The two important time intervals ~ duration-in (entry to exit) and between-visit (exit to entry) ~ which characterize different stages of nesting, are variable during nest building.
Not all approaches end up with an entry to the chimney. It is important to repeat the all-important caveat “interpret the bird’s behaviour in the context of what is happening in the Chimney Swift’s environment”. You should be aware of typical behaviour for a specific stage of nesting vs. behaviour that results from disturbance. If somebody is working on a rooftop and pops up like a Jack or Jill-in-the-box as a Chimney Swift approaches, you should not be surprised to see the bird veer off and avoid an entry!
To recap the “Rules of Feather” for behaviour and activity seen during the Nest Building (+egg laying) stage: there is a lot of variability in the activity pattern at nest sites; daytime entries by a single Chimney Swift or a pair flying together will occur; 1-2 entries and exits per hour are made; and the duration-in/between-visit time intervals are variable.
For my next nest site update, I’ll review late nest building/egg laying behaviour and how to recognize the transition to incubation. Until then, try to get a handle on nest building efforts at your nest site by June 3-4.
The promise of spring is with us now – sunshine and higher temperatures are on their way. As Ken W. in Dauphin commented, the recent rains could ripen a super load of insects for the birds to feed on. As more Chimney Swifts move into Manitoba, the action will increase at your roost and nest sites and maybe at the insect repellant sales counter! We’ve had continued reports of Chimney Swifts in Winnipeg, as well as in Souris since our last blog post. Let us know what you observe!
“Stay Calm, Be Brave, Wait for the Signs” (Thomas King, Jasper Friendly Bear, and Gracie Heavyhand, Dead Dog Café).
— Barb, still swift-less on the Isle of Stewart in the flooded Red River Valley.
