Friday, May 17, 2013

Cap Sante Hilltopping

In my hometown of Anacortes, there's a nice park on a hill called Cap Sante.  Looking to the west from the summit of Cap Sante you get a great view of downtown Anacortes and the Cap Sante marina, as shown below.  The marina services both pleasure boats and commercial fishing boats, many of which fish for crabs and salmon in Alaska.

Downtown Anacortes as seen from Cap Sante.

Cap Sante is also a great location for watching sunsets:

Sunset from Cap Sante, in Anacortes, WA.

In addition, if you look to the east from Cap Sante, you get a magnificent view of Mount Baker, a 10,781 ft high volcano in the Cascade Mountain range.  Here's Mount Baker as seen from Cap Sante:

Mount Baker in the North Cascades, as seen from Cap Sante Park in Anacortes, WA.

What does Cap Sante and its wonderful views have to do with dragonflies?  Well, Cap Sante is a good place to observe hilltopping – a behavior where a group of dragonflies (or other insects) gather in considerable numbers above a prominent feature in the landscape.  In some cases, hilltopping is said to be a reproductive behavior – a way for insects to find mates.  In the case of the dragonflies at Cap Sante, it appears to be a gathering of immature individuals who are feeding together in a loose swarm.

The dragonflies at Cap Sante are mosaic darners, and they are clearly feeding as they fly back and forth over the top of the hill.  The darners really don't interact with one another – they seem focussed on feeding and maturing, before going back to a lake or pond to find a mate.

Here's a compilation of some slow-motion videos showing darners hilltopping over Cap Sante with Mount Baker in the background.  The dragonflies fly and soar almost like hawks.  Notice the interesting flight maneuver at about 18 s, where a darner snags a meal.

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