The Spaniard, undoubtedly frustrated with title-lacking life at Ferrari after five years, might be on the move and Honda is clearly on the hunt for a top driver to spearhead its new works McLaren foray.
"Happy birthday to @alo_oficial," McLaren said on Twitter, adding a photo of Alonso "driving flat-out in his McLaren MP4-22 at Magny-Cours in 2007."
Miguel Sanz, the Spanish correspondent for Marca, commented: "You can't say McLaren and Honda aren't trying or persistent.
"It is the second public nod to Alonso this year and, in this F1 world of millimetres, the gestures are no accident," he added, referring to a McLaren 'tweet' earlier this year showing Alonso smiling with team supremo Ron Dennis.
After the Dennis tweet, a team source played down the significance of the gesture but it is obvious that if Alonso is on the market, he will be bitterly fought over.
For the record, Ferrari marked Alonso's birthday with a celebratory video made in conjunction with Sky Italia, highlighting "all the best moments of his time to date with the longest-running team in formula one".
"In the past four and a half years there has been happiness and disappointment and a lot of time spent with special people, special like Fernando, a truly great talent and a real team player," Ferrari said.
Marca quoted Alonso's former manager Adrian Campos as saying: "Fernando is the best thing about Ferrari -- and I would say almost the only thing.
"He is the most complete driver of recent years, almost comparable to Senna."
But with dominant Mercedes all locked up for now and Red Bull struggling with an underpowered engine, Alonso's best option for now is probably to stay with Ferrari.
"For me, Alonso has justly lost confidence in Ferrari," Marc Surer, a former driver turned commentator, told Speed Week as he mused the 2014 silly-season.
"But he could only move to McLaren-Honda if they can guarantee him a winning car for 2015. I guess a lot less will happen than we think," he surmised.