Understanding Migration at Beamer

Figure 1

Raptors use thermals to move across the landscape efficiently, by rising on hot air, then gliding until they find the next thermal. The thermals get more productive throughout the day, so the birds get higher on the mid-day thermals, and potentially get high enough to exceed the typical human’s visual range! 

Figure 2Cool air settles on Lake Ontario overnight, creating cooler air breezes that hit the Niagara Escarpment most days. Prevailing southerly or westerly winds from the Jetstream push warmer air towards the lake, and the two meet along the Niagara Escarpment. Combined with warm air rising off the rocky cliffs and other ambient thermal activity, these all combine to create a long line of rising air, which runs the length of the Escarpment. Some days when there is little thermal activity, the updraft along the ridge is still present, and raptors follow this, a bit like a surfer follows a wave, efficiently moving north each spring towards their breeding grounds.

Figure 3

The conditions depicted in Figure 2 improve throughout March and April due to the higher angle of the sun’s passage, and increasing day length, producing greater solar radiation and increasing thermal activity. There are lots of reasons raptors return to Ontario in March and April, but traveling efficiently is essential to survival.

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