What’s got the robin so agitated?

DEAR JOAN » As I write this, there is a robin in the tree outside my window that has been calling an agitated call for at least 10 minutes.

During that time, I have seen a hummingbird buzz around the robin numerous times, checking out what is up, and a couple of perching birds that looked in silhouette like tufted titmouse — but I know they do not range here — also coming in seemingly to see what has the robin so agitated.

It is about 6 p.m. in Sunnyvale when this drama is playing out. Do you suspect there is a hawk in the area or something similar, or do you have a different hypothesis? It is just puzzling and it has my indoor cats fascinated. — Janis Brown, Sunnyvale DEAR JANIS » Your theory is a good one, although the threat the robin sees could be something less intimidating than a hawk. It could be the hummingbird.

Birds defending their territory, nests and offspring can get agitated and aggressive with little provocation. If the hummer was getting too close to a nest, the robin could be giving it what for. The robin also might have detected a cat skulking nearby and was telling it to scram.

Male robins often are at their nosiest right before a brood is set to hatch. They are warning other birds to stay away. DEAR JOAN » We had around 50 plums on our tree ripening nicely one day and the next day they were gone. No pits, no stems, nothing. That was about a month ago

Now this week, the same thing happened with our apple tree. All the fruit gone and no sign that the apples were ever there.

These trees are in a fenced backyard. We have noticed large black birds in the area and we have squirrels, but what is strange is that all the fruit disappeared the same night.

Any clue who the culprit might be? — Kathy Morte, Bay Area DEAR KATHY » My first and favorite choice is squirrels. They are more likely to grab the fruit and make a run for it. They also like to stockpile their groceries, which would explain why you aren’t finding any evidence.

However, if you are certain the thefts are occurring at night when the squirrels are tucked into bed, the focus changes to nocturnal creatures such as rats, raccoons, opossums and foxes.

My faithful Chihuahua, Bailey, recently caught an opossum redhanded in my plum tree. There was a whole lot of barking that ended up with the opossum playing dead and a confused Bailey trying to figure out what happened.

It does seem odd that you don’t find any signs of the fruit, which would indicate you have many creatures harvesting your tree, or a two-legged varmint has entered the picture.

Keeping critters out of your tree won’t be easy. You can start by pruning limbs away from fences or structures, and loosely wrapping tree trunks with metal flashing or installing a baffle to prevent animals from climbing up.

While netting can keep birds out, it’s less effective on creatures with sharp teeth that simply gnaw through the net to get to the fruit.

Are others seeing their fruit disappear mysteriously? If so, I’d love to hear about it, as well as your theories on what animal is to blame.