"You can't have two robins on your bird-table," Rachel assures me. "They're territorial birds. If you had two robins in your garden, never mind on a small piece of wood together, they'd be ripping each other's feathers out."
"Let me get this right," I say. "You're 500 miles away on the end of the phone and I'm looking out my back window at a bird-table six feet away. But you know better than me what's on it?"
"Sounds like it," she says. "Could one of them be a chaffinch?"
"No," I tell her. "One of them couldn't be a chaffinch. It's two robins side by side, happily pecking the bread I put out for them."
"Maybe one of them's a bullfinch," she says. "They have red breasts too. Easy mistake to make."
If Rachel has a fault - and I'm not saying she has - it's over-reliance on her own brain at the expense of mine. Normally it's not a problem. But when she doubts the evidence of my senses it's mildly irritating.
"No!" I tell her. "One of them couldn't be a bloody bullfinch. I know what they look like. This is two robins. Get over it."
The line goes quiet, then "Aha!" she cries. "I've got it. Take another look at your robins. I'll bet they're mincing about with their hands on their hips."
"They're gay," she tells me. " You've got gay robins. They've set up home together in your garden."
"Bollocks," I say. "There's no such thing as gay robins."
"Shows what you know, pal," she says. "You get homosexual behaviour in loads of animals - swans, penguins, mallards, vultures, dolphins, apes, lions, lizards, sheep, goats. In one study, over 90% of giraffe mounting was male on male."
"If I had giraffes on my bird-table I'd have noticed," I say. "I have robins. And they're not gay."
"You're in denial, son, maybe even homoerithacophobic. Take it from me - if you have two male robins on your bird-table they're gay."
I ponder this while watching my birds surreptitiously through the back window. They seem straight to me. "Is there some way to tell for sure?" I ask her.
"Other than catching them in the act, only one way I know," Rachel says.
"Look out an old Elton John song, play it loud and open the window. If your robins start bopping on the birdtable, they're as gay as pink pants."