Using Radar to Find Birds (and Fish)
February 11, 2011
When using radar to find birds working over fish, there are a few things to consider. The first are radar power and display screen size. I currently have a 4 kilowatt (kW) Raymarine E-Series unit aboard my boat. Four kilowatts is generally considered too weak for detecting birds; however, the situation changes when you combine that power with a 12″ color display, which increases the amount of detail you can see.
A 2 kW unit, which is common on small center consoles, is usually too small to pick up birds effectively. Likewise, a 4 kW unit combined with a small screen may be able to detect birds, but they won’t show up very clearly on the display.
If you’ve never used radar to find birds, start by practicing on a calm day. Fog and glare don’t matter, and will actually help improve your bird-detecting skills. Also, keep in mind that the optimum gain and clutter settings will vary according to your make and model of radar.
With my new Raymarine E-Series unit, I start by setting the rain and sea clutter settings to zero, then slowly start to increase the gain. I have found that a gain setting of 63% to 68% is best for marking birds without getting too much background clutter. I know I’m at the right level when I start to see a few stray specks on screen.
Once I’ve got the gain dialed in, I usually set the radar to the 1 1/2-mile setting. I use the “offset” mode and position my boat at the bottom of the screen, so I have about 2 1/2 miles in front and on either side of the boat and about 1/2 mile behind the boat. I can also use the 3-mile setting and push the gain a bit higher to scan a greater distance. I’ve even been able to pick up birds at 4.8 miles, but that’s really pushing the limits of the unit and my interpretive skills.
Running with Radar
If I’m running a shoreline, I’ll offset the boat to the bottom of the screen and off to one side, so I have the “short side” just hitting land and the longer range sweeping the water. This allows me to cover an area like Buzzards Bay in about 30 to 45 minutes (generally 2 full passes over the bay).
My older Furuno NavNet unit required a different tuning procedure. I would start by setting my gain to manual 100%, rain clutter to zero and sea clutter at between 60% and 70%. At sea clutter settings above 60% I would start to loose a lot of detail. Most of the time I would be at around 50% to 53%. As I pointed out earlier, it all depends on your particular make and model.
Next I would set the radar range at 1 1/2 to 3 miles and begin my search. When I picked up something that looked suspicious at the 3-mile range, I’d head in that direction until I could home in at the 1 1/2-mile range. At this point I could generally determine if the object in question was a flock of birds or not.
A flock of birds looks like a sponge on screen. The shape does not register as a solid hit, like a buoy or a boat. It is amorphous, changing shape like an amoeba with every sweep of the radar.
Dialing in Gain
The best way to hone your bird-detection skills is to practice on a clear day with good visibility. Find some birds, then move off a mile or so and see what they look like on the screen. Play with the settings until you achieve the best picture, then remember those settings (it helps to write them down). Start with all your settings at zero then increase the gain incrementally until you begin to mark the birds. Keep increasing the gain until the clutter gets too dense to see the birds. Now decrease the gain until you start to see the birds again.
You can tweak the sea and rain clutter settings too, but I find that it’s best not to use these filters.
Once you find a good flock of birds to practice on, you should be able to find a baseline setting and then fine-tune from there. For example, from the baseline you may want to tweak the clutter a few degrees up or down based on sea conditions. However, I’ve found that my settings never vary much from the baseline.
It should be noted that different types of birds show up better on radar than others, and more birds are better than just a few. However, it is possible to pick up single birds on a 4 kW radar and a big display if you know what to look for.
What’s really nice about using radar to find birds is that it gives you a better overview of the flock. With binoculars, you only see the leading edge of the birds; you can’t tell how dense the flock is until you get closer. With radar you get a top-down view, allowing you to determine the shape of the flock, its size and, most important, its density. The denser the flock, the more intense the feeding activity of the fish below. In this sense, radar can save you a lot of time and fuel in your search for a big flock of birds feeding over fish.
Is there anything else you’d like to know about using radar to find birds?
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