Finding a fallen tree might be sad, but it's a great opportunity to learn more about it "from above"!
This is a birch (Betula pendula) heavily infested by the parasitic mistletoe (Viscum album), itself a host to numerous fascinating species.
Here we have some pretty, little Gossyparia spuria. This is a generalist parasite that can be found on several other kinds of plants too.
Sphaeropsis visci, or more lengthily Phaeobotryosphaeria visci. We can see a contrast between the green, healthy leaf and the yellow, dying tissue sprinkled with the pycnidia of this hyperparasitic fungus.
I can never get a good shot of these cutest little critters. Cacopsylla visci is a psyllid that thrives only on V. album. These are the nymphs.
A mysterious leaf mine that (to my knowledge) could only've been dug by the elusive mistletoe marble moth (Celypha woodiana). Sadly, I'm yet to see the actual moth and I'm not aware of its records in my country, so the ID is tentative until then.
Lastly, we have a wood wasp (Xiphydria sp.) ovipositing into the birch. The larvae develop in dead and recently fallen trees, boring tunnels through the wood and dispersing a symbiotic fungus which provides them with nutrition and helps accelerate the tree's break down. That's right, these wasps are a little symbiotic wonder! The fungus in question can be either or both Daldinia decipiens and Entonaema cinnabarina depending on the species. Female wasps even bear a mycangium – an organ that carries these fungal mutualists. More on this fascinating relationship here.
