Ville fielded three new faces in their top six for the Division 2 curtain-raiser - Kiwi overseas signing Josh McGregor, former Havant and Purbrook all-rounder Josh McCoy and ex-Liphook batter Gabriel Broadhurst.
But after that trio only managed 21 runs between them, Birch and Shepherd took centre stage.
They came together with Ville 87-5 in the 25th over chasing what at the time appeared a distant 215 victory target at the Green Jackets ground in Winchester.
But Birch (68 not out) and Shepherd (55 not out) added an unbroken 128 for the sixth wicket as the visitors won with nine balls remaining of their 50-over allocation
It was Birch’s career best Southern Premier League score, with his only higher innings of 74 coming in a pre-season friendly against Littlehampton three years ago.
Birch hit seven fours in his 76-ball knock while Shepherd counted four boundaries and a six in his 85-ball stay at the crease.
Former Hampshire batsman Steven Laney had earlier underpinned St Cross’ 214-7 total. Opening the innings, the home skipper hit 77 in a 130-ball stay before he was caught by Charlie Jackson off the bowling of Ville skipper Archie Reynolds.
It was certainly an all-round bowling effort. McCoy took 2-28 off six overs with five other bowlers chipping in with a single wicket. Sam Hillman, who shared new ball duties with McCoy, was the only bowler used who didn’t take a wicket - but he only conceded 19 runs off his 10 overs.
St Cross, who had finished bottom of Division 1 last summer, had reached 161-2 - Michael Haworth 44, Steven Hirst 29 - but didn’t kick on from that promising position.