Swallowtail and Dragonfly Perch Preference

[Dinusaur]

I was sitting by a storm water pond in Markham when I saw a duel between a male Blue Dasher and a male Eastern Amberwing dragonflies over a particular perch. They were constantly chasing each other away from this specific perch. What is in this perch that they both preferred? Don't know the exact answer. There appears to be a large volume of research conducted on perch preferences by dragonflies - larger dragonflies prefer higher perches whereas the smaller ones are ok with lower perches. These two dragonflies are almost of the same size, may be that was the reason that they both wanted to sit on the same perch. There were a bunch of damselflies right below them and they didn't bother them at all. As I was about to leave I saw a Spicebush Swallowtail butterfly - I am not sure if I have seen one before. That was icing on the cake.




Spicebush Swallowtail. Can anybody tell if it's a male or a female?

[Ally]

I don't know the reason, but I have to comment on how great the shots are!

[Shortsighted]

When there is competition for a perch why not change the dynamic by introducing yet
another perch alongside, or at least near the coveted original item. Does the perch
have a scent? Is the preference one of height, perch length, perch direction or perch
material?

[Ally]

I don't know all the reasons, but I found one of the reasons.