Teleconverter as an ID aid? UK (1 Viewer)

Sorry, no bird to ID, just a quick question. I'm considering splashing out on a 2x teleconverter to use with my 500mm zoom, not with expectations of quality images, but as another tool to help with the ID of any long distance waifs and strays sighted that have ID doubts. Has anybody done this, and, if so, has it been useful or is observing through a scope and noting down the birds features,plumage etc, still the best option?
I find using the 500mm to help with Id's quite useful, as the image shows. What I thought were two long distance buzzards turned out to be a buzzard and a marsh harrier, wondering if the results using a teleconverter would be any improvement?
Thanks in advance for reading.
Joe

Adding a 2x to a 500mm lens will give you the shakes big time - unless you can generate a very fast shutter speed (c. 1/1250 or at least 1/2000 if you're on a crop-sensor body)and/or use a tripod!

You will lose 2-stops adding a 2x and not all 2x converters are compatible with all lenses. Dependant on your set-up, you will probably also find that you will only get manual focussing at f/8 at best.

You might want to consider the 1.4x - that will give you 700m native or 1120m effective field-of-view on a crop-sensor, and will also retain auto-focus if your 500mm is a f/4 - but not if it's f/5.6 or greater...

Nonetheless, given those limitations, I also find that if I can grab an image, that's generally a far better means of ID'ing something "odd" than trying to scribble down what I see, and then rely on memory later in the day for book searching! Horses for courses!

Good luck...