Observation: In past years, Tree Swallows (Tachycineta bicolor) arrived in early April and then increased in numbers so one could see them everywhere. This year, I saw only 3 on May 7th. Then nothing. I don't see any swallows this year for first time ever. - John Disney, Economic Development Officer, Masset, Haida Gwaii.
Comment by LEO BC Coordinator: Tree Swallows (Tachycineta bicolor) have an extremely broad range and are highly abundant overall, and so have a Red List Category & Criteria: of 'Least Concern'. This species is also known to undergo declines and extreme fluctuations in its area of occupancy (Birdlife International 2016). Dr. David Bradley in his contribution below has suggested that lower temperatures can reduce prey availability. In fact, the daily data report from the Government of Canada for the ADDENBROKE ISLAND station shows freezing temperatures in January, February, and March of 2017, so perhaps this influenced the flying insects in the area as Dr. Bradley suggests as a potential explanation. However, that temperature station is on the Central Coast and not on Haida Gwaii. It is also possible that due to the anomalously warm summer temperatures over the last 3 years, tree swallows are rapidly shifting further north for breeding. Both shifts could relate to changes in the timing or distribution of their prey species. - Tom Okey, PhD., Ocean Integrity Research and UVic Environmental Studies.
Consult by Dr. David Bradley: Tree Swallows are aerial insectivores, so they feed on flying insects. If the insects are absent from an area then the birds will move off elsewhere to feed. I don't know what the temperatures on Haida Gwaii have been like this spring [see link above], but if they are low this can suppress the insect hatch and therefore the availability of swallow food.
It does seem unusual that swallows that are normally present in most years would not be present this year. I checked eBird and there have been a few seen around Tlell, Sandspit and Queen Charlotte, but none around Masset. I will be monitoring eBird to see what happens in the near future. - Dr. David Bradley, British Columbia Program Manager, Bird Studies Canada.
References:
BirdLife International. 2016. Tachycineta bicolor. The IUCN Red List of Threatened Species 2016: e.T22712057A94316797. http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22712057A94316797.en. Downloaded on 23 May 2017.
Observations From Members 