More marsh management

We ran out of heating oil this weekend. This time last year it would have been a disaster, this year it's a minor inconvenience. The continuing mild weather is great for the birds although not so good for birding with very few waterfowl locally apart from our usual wintering Teal flock. Its easy to believe spring is not far away despite it being only mid-January and the local flora and fauna are adding to that feeling.
In the garden Hazel catkins are in full bloom, Snowdrops have speared through the fallen leaves under the trees and are about to burst in to flower, and Daffodil spikes have appeared in the lawn. The Rooks were back in their rookery today, not just one of their brief early morning forays but a full days noisy checking out of their old nest sites. Cuckoo Pint is starting to erupt in the hedgerows, Winter Gnats were dancing and Song Thrush and Great Tits were blasting out their songs. There's still plenty of time for a cold snap but at this time of the year it can't possibly last too long.
Yesterday we had Mark Smart, the warden at RSPB Berney Marshes, visit to give us some advice on improving the marshes to encourage Lapwings to breed. We need more foot drains, not to drain the marshes but to provide some persistent damp areas for Lapwing chicks to feed. As we've got the ability to control the dyke levels in the internal dykes on our land we've got some ideal areas and the RSPB are happy to come back in August (its too wet for a tractor right now) and cut them for us. We have to pay but I'd rather pay the RSPB than a contractor and if the RSPB do it we know the drains will be cut to the correct size and in the right place.
My Patchwork Challenge list has had only 2 additions since last weekend, the afore-mentioned Song Thrush and a calling Wigeon in the dark yesterday evening, despite much effort outdoors. Marsh Harrier CN (see January 11ths post) re-appeared today after going missing for 2 weeks. She was calling  using the high-pitched sound I usually hear between breeding birds in the spring. Would any one know if this is a sign of potential breeding activity?