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Hummingbirds begin astounding migration

2018 09 22 hummingbird small

By David Hawke - There is a fascination with migration that shows up every autumn.

 Whether it be a monarch butterfly of a Canada goose, there are those amongst us who watch with abated breath to see if critters can escape 'certain death' if they tarry too long and tempt their fate against a dreaded 'cold snap'.

          Over the past week I've heard from three people inquiring as to the seasonal movement of hummingbirds. And I get it, as these little feather bundles are renowned for their reliance on flower blooms to sustain their life. Once the flowers die off, what in the world will a hummingbird do? Good question, but Nature has had this riddle figured out long ago.

          The obvious answer is to fly to where there are still flowers in bloom, somewhere way down south. But these little overachievers don't just go to Florida, they go right on across the Gulf of Mexico to Central and South America. That's 800 km over open water, a 20-hour flight!

          There has been much speculation as to how these tiny birds manage to complete this epic crossing, with ideas ranging from that they hitch a ride on the back of larger birds to riding hot thermals of air. Tests have been conducted using wind tunnels and carefully measured food, subjecting hummingbirds to simulated flight times. Bottom line is, so far, we don't really know for sure yet just how they do it, other than they do miraculously show up on the distant shore with each migration (although the avian hitch-hiking idea is widely poo-pooed by the scientific community).

          Storing enough energy in their body fat is tricky balance between extra weight and having enough fuel to carry on. It takes about one week of feeding to gain the calories required for a leg of the trip. After flying to near exhaustion, the birds stop and feed for a few days to gain strength for the next flight.

          A hummingbird weighing four grams needs to take on the equivalent of 1,400 calories per kilogram, while a 120-gram mourning dove may take on 127 calories per kilogram over the same time period. Which shows that hummingbirds really burn up their fuel and need to replenish much more frequently than a dove.

          Many people plant nectar-rich flowers in their gardens for hummingbirds to use as a food source, while other may elect to install hummingbird feeders. Artificial feeding stations work well, as long as you follow a simple rule: mix the sugar solution at 4 parts water to 1 part white granulated sugar. Do not use brown sugar, maple syrup, agave, molasses, or honey... these all contain fructose which is bad news to hummers.

          Feeders may be left up (cleaned and refilled every couple days) well into the late summer. As the birds migrate south they will visit to gain a nutritious snack while enroute. A few folks take their feeders down in early September, fearing they are luring the local hummers to stay too late, however research has shown that the birds will leave when influenced by natural factors such as reduced photo-period, falling temperatures and lack of flowers as a food source. Your feeding station is like a corner convenience store for a last-minute snack.

          An interesting note about birdwatchers and hummingbirds is the detail in which spring arrivals are noted, compared to the last date observed. Several years of records show the birds swooping into our region between April 20 and May 8. I couldn't find any records on departure dates (but maybe I didn't look deep enough?). Check out www.hummingbirds.net for maps of arrival dates across North America.

          While these small birds are tough enough, they are at risk from a strange peril: burdocks. The hooked burs can latch onto their small feathers and hold them helpless. So how does a hummingbird even come close to a bur? By foraging for insects caught in spider webs, webs which are commonly constructed in the branches of burdock. I have found a dead hummer in such a predicament, as well as there have been several reports of this happening from a park on the Toronto shoreline.

          This warm weather is allowing the hummingbirds to continue feeding on the last blooms of cardinal flower and jewelweed, building up their energy reserves for the flight they know is to come. Barring the occasional hurricane crossing their flight path, the hummingbirds should be on their way to points south any day now.

David’s Notebook: The back-and-forth weather has signaled to the monarchs and hummingbirds that it's time to go. Amazing migrations each will take, despite one being an insect and the other a bird. Nature astounds us!

© 2018 David J. Hawke

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Sunday, 21 October 2018

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