Marsh Tit - Monsal Dale

The Marsh Tit is the least common member of the tit family in Derbyshire, it was reported from just 25 locations in the 2014 Derbyshire Bird Report compared to 62 locations for the Willow Tit. This is the reverse of the national situation where there are estimated to be six times as many Marsh Tit territories as there are for Willow Tit (52,800 and 8,500 respectively in 2000).
Sadly both species have suffered a more than 50% population decline since the 1970's and both are now red listed as species of most conservation concern in the UK. 
I photographed this bird this morning in a very gloomy and damp Monsal Dale.

Marsh Tit

The Peak District holds a significant proportion of the Derbyshire population and Monsal, Millers and Chee Dales are still amongst the best areas to listen for its distinctive 'pitchou' calls which are the best way of separating it from its very similar cousin.
Various features have been suggested for separating the two species; the Marsh Tit tends to have a smaller bib and a dull rather than glossy black cap but these features are often unreliable or difficult to determine on a lone bird. 
A pale mark above the cutting edge at the bill base in Marsh Tit has been relatively recently described (2008 and 2009) as a reliable way of separating the two. Where present this may be helpful as shown in photo above and the cropped image below.

Marsh Tit on left showing pale mark at base of bill generally absent on Willow on right

Marsh Tit (left) and Willow Tit showing the black bib

Pale edges to the secondaries and tertials form a pale panel in the wing of the Willow Tit which, when present, is a good indicator of Willow as can be seen in the photo below taken at Carsington on Friday. 

Willow Tit

Locally the best places to look for Willow Tit are the feeding stations at Carsington and Ogston Reservoirs or slightly further away at Carr Vale.
There are occasional Willow Tit records from Flash Lane, Darley Hillside and Clough Wood but I have never come across Marsh Tit in the immediate Darley Dale area.