One of my most used settings on the camera is the Exposure Compensation!

Exposure compensation is a technique for adjusting the exposure indicated by a photographic exposure meter.
Wikipedia

If you set up your camera as I do set the Aperture, ISO on auto, and then adjust Shutter as needed for the composition. Set up like this the quickest way to adjust exposure but still keep your shutter speed and aperture settings where you like is exposure compensation.

This comes in handy for so many use cases:

• Sunsets and Sunrises.
• Darker or Lighter subject than background.
• Birds in Flight.
• Birds in trees with sky backdrop.
• Moon shots.
• Or even making a background darker.
• The list goes on…

Negative Exposure Compensation

The following gallery of the moon photos shows how using the exposure compensation setting can easily change the exposure of the photos. Using negative exposure compensation with a subject like a moon can really bring out shadows showing more texture and depth.

All of these photos were taken handheld with a Nikon D810, Sigma Contemporary 150-600mm f/5-6.3, on Manual mode.
Shutter: 1/800 seconds and Aperture: f/10.0. Focal Length: 600mm and Cropped 74%.

Because my ISO was set to auto you can see it creep for each exposure change.

You can use this same technique to bring out the color with sunsets when there is still a bit to much light.

Positive Exposure Compensation

My most common use is for birds flying with the sky as the background then you add some positive exposure. If I know my target is going to be flying birds I almost always add exposure compensation +0.7 from the start and usually end up at +1.0 to +1.7 depending on how bright of a day it is. This makes sure we get enough exposure on the bird, otherwise, it will just be a slightly colored silhouette of birds flying.

Male & Female Blue-winged Teal Ducks

Alternative Options
1. You could change to spot metering instead of exposure compensation, but then you have to try and keep the bird in the metering zone of the focus point. This can be quite difficult with flying birds that are fast like smaller ducks.

2. Another is shooting in a priority mode but I personally prefer manual mode.

But, I prefer sticking to Manual mode and with auto ISO so I can adjust quickly on the fly (pun intended). There are times where I switch to manual fixed ISO, like waterfalls, astrophotography like the Milkyway, and most of the time sunsets even though exposure compensation would work for sunsets just fine.

The key to all of this is practice and lots of it so you know your gear and what it can do!

If you have any questions feel free to ask in the comments.