I am new to GIS so excuse my lack of proper terminology.
What I would like to do is to calculate a mean DNI (direct normal irradiance) for multiple bird species. I do find a DNI-raster online (https://solargis.com/maps-and-gis-data/download/world) and have a multipolygon (?) containing species-presence polygons (available from birdlife). I've added a picture of the layers to ensure that my terminology is correct.
I would now like to create an attribute that is basically the mean irradiance a bird species would receive given the DNI that its distribution range receives. What I envision is that this would mean that each "pixel" the species occurs in should be multiplied by its corresponding DNI value. Next all these "pixels" should be summed and then divided by the total amount of occurence-"pixels" for that species. I am just not sure how to do this.
I hope the question is clear, and that someone could help me with this.