Many animals engage in “diel” behaviours. ‘Diel’ is a science-y term that refers to a cyclic 24-hour pattern of behavior usually related to day and night patterns (can also include twilight periods). Owls are a good example of a group of species that exhibit diel behaviours, typically sleeping/inactive during the day and foraging at night. Jaguars and other big cats are more examples. Sardines will migrate vertically in the water column to forage, going deep during the day and rising toward the surface in response to zooplankton movements.
The latter sardine example illustrates both diel behavior and a migration. We often think of migrations as being for reproduction (e.g., Pacific salmon), but a migration can be any directed movement between at least two discrete habitats. So, for sardines, moving from the deep ocean toward the surface would be considered a migration. Ducks escaping frigid north latitude temperatures and moving long distances to warmer locales would also qualify.
Here in Charlottetown, Prince Edward Island, we have eastern crows that migrate every day from their roosts to their territories and back again. They fly the exact same pathways into and out of the city, leaving at dawn and returning at dusk. A lot of crows on PEI (clearly not all, but certainly several thousand… a “murder of crows” if you will) roost in Victoria Park, one of Charlottetown’s biggest attractions for locals and tourists alike. At night, they roost in the trees IN TOTAL SILENCE. Creepy doesn’t even begin to describe what it feels like walking underneath a giant tree with hundreds of sleeping crows 50 feet above your head. Then, in the morning they disperse to their colonies, forage during the day, and fly back to their roost at night.
I went for a walk yesterday evening originally to photograph the landscape around Charlottetown, but when the light was uncooperative I turned my focus to the crow migration happening over my head. Some hate crows, but I find them fascinating creatures. We once had a bag of compost that we set out overnight on our deck. In the morning we woke to find chicken bones, which were buried half-way down in the bag, scattered about the deck. Upon closer inspection of the bag, the crows had pinpointed the location of the chicken bones, poked holes just barely large enough for their beaks to fit through, and carefully extracted their prizes. Indeed, crows are creepy smart. If you don’t believe me, just watch this video of crows using tools.