Why it’s worth noting flying and flight direction

Look! Up in the sky! It’s a bird! And it’s flying southwest!

For a long time now I’ve been noting down the direction birds fly. It’s baked right into my Wildtype Shorthand. For example,

Blk shag fm_ne1f_sw

That means one black shag first seen far (80–320 m) to the northeast, getting as close as mid (20–80 m), and flying southwest.

Why go to the extra bother of recording whether a bird is flying, and the direction it’s flying? There are a few good reasons to add these details.

First up, it’s useful to distinguish flying birds from birds that land because this tells me which birds are using the habitat I’m in, and which birds could be just passing through. The black shags I see over New Zealand suburban housing are just passing through. The condition of the local habitat is irrelevant to them. That’s quite different from the birds that land and use the habitat for their livelihood.

Changes to the condition of the local habitat can change my counts of the resident birds, but shouldn’t change the counts of birds flying by. Any trends in my counts of birds flying by will be influenced by things going on elsewhere. It’s useful to be able to keep these separate in my wild counts.

Separating off flying birds is therefore helpful, but why also note the flight direction? I have several reasons for doing this. The first is that if a bird is circling above, it may still be using the habitat of that location. For example, welcome swallows circle about overhead catching insects, seeming to spend most of their days on the wing. An Australasian harrier can circle overhead searching for its next meal below. However, a black shag flies in a straight line overhead. Birds flying circling can therefore mean something quite different from a bird flying a set course overhead.

Other than circling, why note the flight direction? For some birds in some situations I admit that it’s likely of no value at all. For others, however, it has given me extra insight into their lives. The black shags I see flying over our house tend to be either flying northeast or southwest. It turns out that we live on a wetland bird flyway between Christchurch city’s Avon-Heathcote estuary and Lake Ellesmere/Te Waihora. These birds are passing overhead between two suitable habitats. If a new, suitable wetland habitat was established in the city, this would likely be reflected in a change in flight directions by these wetland birds.

Black-backed gulls, in contrast, tend to fly northwest or southeast over our house. They are coming and going between the city and the gull colonies in Lyttelton harbour over Dyers Pass in the hills to the south.

By paying attention to flight directions, I have also started to notice the daily cycles of birds. For example, at some times of year, New Zealand’s wood pigeon, the kererū, tends to fly down out of the Christchurch Port Hills in the morning and back up into the hills in the evening. I see these birds foraging on fruit and leaves of city trees. This flight pattern suggests that many kererū return daily to the hills to roost. No GPS tracking was required to figure this out. I just had to note the flight directions.

Flight directions also help more generally with estimating counts of birds. If I see one black shag flying southwest and then another flying southwest shortly afterwards, I can be confident that I’ve just seen two black shags. That’s not the case if I see one bird flying southwest and another flying northeast. Those could have been the same bird that turned around. Noting flight directions helps me to figure out how many individuals I mostly likely saw.

Smart phones make it easy to note flight directions. Most smart phones include a compass, making it simple to accurately remind yourself of direction. With few exceptions, I also keep things simple by just noting the flight direction to the nearest 25° (north, northeast, east, etc.).

So, there you have it. If you’re out watching birds, there are benefits to paying extra attention to the birds flying by and the directions they’re flying. That’s quite aside from the general “wish I could do that” astonishment I still get from seeing birds in flight.