Generally speaking, looking at bird photographs isn't really our thing, but our sense of aesthetics is not shared by all. Bird photography is the new craze, with the common use of multiple flashes employed to freeze those hummingbird wings cycling at 80 flaps per second.
The Audobon Society, ornithologists and other conservation groups, however, urge photographers to minimize or to eliminate altogether the use of flash when photographing birds.
Although flash photography at night has been shown to disrupt a bird's ability to hunt for food, the evidence linking the use of flash during daylight hours and harm is less certain. Unfortunately, most of the studies were confounded by small sample sizes and observer bias. On the other hand, a study on the West Indian anole (Huang et. al. 2015) demonstrated a marked alteration in the bird's behaviour caused by the camera shutter slap alone. Birds are very easily stressed and changes in serum cortisol in addition to increased NMDA signaling in the periaqueductal grey matter (a fear trigger zone) is easily elicited by even the slightest of stressors. Birds under stress have a mortality rate more than ten times the population norm.
As it stands, until there is more evidence from which we can arrive at consensus photographers should view bird flash photography as harmful and disruptive until proven otherwise.
The ethical foundation that should guide all nature photographers is to do no harm. Although this may seem self-evident, unfortunately, more than a handful of nature (and bird) photographers are not in the least bit concerned about what harm their activities may inflict upon wildlife. This apparent irony stems from nature photography developing as a substitution for hunting for sport. Indeed, photographers 'hunt with the camera' and this phenomenon has been known to psychologists since the turn of the twentieth century (Dunaway 2000).
To the photographer, the trophy is the print hanging on the wall, not unlike the trophy heads that adorn the walls of hunter cabins. As the adverse societal pressures against the white aristocracy's habit of hunting for sport mounted in the mid-twentieth century the transition to wildlife photography was fomented. This would lend credence to the notion that ethicality is a foreign language to some nature photographers.
One of the cardinal rules broken by nature photographers is feeding wild animals in order to get the animal in close for the shot. In some jurisdictions, feeding wild animals comes with a jail sentence.
Wildlife and nature photographers should endeavour to care a little less about the perfect shot and a little more about consideration for the animals at the other end of the lens. No trophy is worth harassing and disrupting the lives of creatures who share the planet with us.