The Willow Warbler is classed as Amber on the UK conservation list.
Worcestershire Wildlife Trust
is urging visitors to keep their dogs on a lead to help protect birds.
James Hitchcock, the Trust's reserves officer, explained that dog-walkers can pose a real danger to birds' nests.
"Even the most well-behaved dog will unintentionally scare these vulnerable birds."
James stressed that the Trust still "welcome responsible dog-walkers but would like to remind people to keep to the paths and keep dogs on the lead."
This request is especially important considering the Willow Warbler's fragile existence.
The species declined rapidly by over 35% in the 80's and 90's in Southern England and the Midlands.
This message is particularly relevant as the breeding season will soon begin, starting in April and finishing in July.
This will be an important time of the year for birds like the Warbler, James points out, and it is crucial that dog-walkers and other visitors to Trench Wood bear this in mind.
The summer migrant willow warbler isn't the only bird to be found in the reserve.
It is just one of many birds, including the exotically named blackcap, chiffchaff, woodpecker and nuthatch, that live in the scrubby undergrowth found there.
The large wood is also home to many wildflowers and butterflies.
helped the Trust to purchase the woodland, recognising its importance as an excellent place to spot white admiral, white-letter hairstreak and rare brown hairstreak butterflies.
To find out more about endangered bird species click here