Diurnal Migration Case Studies

Diurnal Migration Case Studies:

Diurnal Migration

Zion Road, Chatham-Kent, Ontario - 23 October 2018

ebird checklist - google maps for location - archived weather conditions - surface map

• Key Species: 

  • Thousands of finches, blackbirds, crows, etc. 

Conditions on this day were strong northwest winds soon after the passage of a front, this concentrated expected diurnal migrants along the Lake Erie shoreline as they attempted to go south (flying southwest down the shoreline). Generally, the majority of these birds are moving in the expected direction at the expected time of year. The recent passage of the front may help preclude the finch species from being considered onward migrants (if overnight conditions were not conducive for nocturnal migration) and the volume of crows/blackbirds etc. supports that they were not undertaking a post-roost flight. 

Other Checklists: 

Chatham-Kent, Ontario - Sep 3, 2023: diurnal migration of Ruby-throated Hummingbirds.

Huron, Ontario - Oct 28, 2022: Expected late fall diurnal migration of southbound birds. Some Evening Grosbeaks moving north/northeast are interesting, as finches may be intending to migrate in more east-west directions than other passerines. 

Return Migration or Failed Nesting

Point Pelee (Tip), Essex, Ontario - 6 June 2022

ebird checklist - google maps for location - archived weather conditions - surface map

Key Species: 

• 1 Bobolink 

• 1 Prothonotary Warbler 

• 2 Pine Warbler

A subtle and perhaps mundade potential reason for a diurnal migration morning flight involves possible failure to nest (either unable to find a mate, or actual nest failure). I've noticed an atypical number of some species such as Pine Warbler and Prothonotary Warbler in morning flight very late in spring migration, suggesting to me that some species utilize late season migration and/or morning flight to either abandon their nesting habitats or seek out new potential territories during the daylight hours. More dramatic examples may involve Bobolink or Dickcissel, which perhaps had their territories destroyed by haying, forcing them to relocate late in the season - occasionally appearing as apparent reverse-migrants in morning flight. What's novel here is that some birds may be intentionally migrating south during the spring, meaning they could well qualify as "true" diurnal migrants or even "onward" migrants (see below), or perhaps undertaking other "types" of flights noted below.