Why does hummingbird nectar turn yellow?

DEAR JOAN » At times the nectar I make for my hummingbird feeder turns yellowish. I just changed this last batch Sunday and Monday it turned yellow and Tuesday it’s almost golden.

I use 1/3 cup ofw hite sugar to 1 ¾ cups of water. Any idea? — Ted, Bay Area DEAR TED » There are some possibilities, starting with your formula. The ratio for hummingbird nectar is 4 to 1, so if you’re using a third of a cup of sugar, you should use 1 1/3 cups of water.

I’m not really sure that’s the problem, however, because you’re giving them a diluted formula, which would be less likely to form bacteria.

It could be your sugar or your water. Make certain you are using pure cane sugar, not sugar made from molasses or any other product. You might have impurities in your water so try using bottled or filtered water and see what happens.

I’d also clean the feeder really well, soaking it in a mild solution of water and bleach. Rinse well and allow it to air-dry. If you’ve had the feeder for a number of years, you might want to replace it as it could be something in the plastic that is causing the discoloration.

Hummingbird nectar can be finicky. It tends to go bad quickly in the heat of the summer, but can become cloudy during the winter rains. Obviously, we want to protect hummers from disease and mold, so it’s always a good idea to keep an eye on them.

I also wouldn’t rule out the possibility that another creature could be drinking from the feeder and leaving behind some contamination.

Has anyone else had this problem? If so, how did you remedy it?

DEAR JOAN » I’m trying to identify the animal that is taking an occasional lemon from our Meyer lemon tree in front of our house. This has happened three times in the past two weeks.

What has me stumped is the really tidy manner in which the critter has done this. It has picked a single ripe lemon from the bottom of the plant, consumed the skin without a trace, and then neatly eaten about half of the pulp. The first one was even neater than this. All that was missing was a thank-you note.

These incidents must have occurred at night or early in the morning. I am rather fascinated with the culprit’s modus operandi, and inclined to let it go on unless there is a risk that the situation will worsen.

So who is our little visi- tor, and what should we do? — Vic Ryerson, Orinda DEAR VIC » Your tidy visitor is most likely a rat. Rodents have a well-earned reputation for eating the lemon peels and leaving behind the pulp. They also will sometimes eat the pulp, but you could have a second visitor — an opossum — that is batting cleanup and eating what the rat leaves behind.

If you don’t mind sharing a few lemons, you don’t need to do anything, but it can get out of hand.

Prune lower branches and loosely wrap the trunk with metal flashing to stop the rats from climbing into the tree. You’ll want to isolate it from other trees and structures to prevent rats from using those vantage points to gain access to your lemon tree.

Clean up your yard to remove food, water and sheltering places that encourage rats to hang around.