I work on the Steelworks on Teesside. The site is situated on the south edge of the Tees Estuary and coast.
It depends on what you mean by "what you have seen at work".
Birds seen whilst going about my normal job include things like Yellow Browed Warbler, Waxwing, Crossbill and common migrants in the bushes behind the office block. Flyovers include Honey Buzzard, Long & Short Eared Owls, skeins of geese etc.
If I can count birds seen on/from the site then it's much better. The fly through Sandhill Crane was seen from the roof of Steel House, the sites main office block. I did get a few strange looks when I dashed through the offices and onto the roof with scope & tripod that day.
Great Knot, Short Billed & Long Billed Dowitchers, White Rumped Sand have all roosted on the site. Lesser Crested Tern, Roseate Terns,Long Tailed Skuas, Sabs Gull have all been seen in the river mouth from the site.
I could technically include South Gare as most of this area is owned by the steel firm. The access road is a private road and is closed one day per year to maintain the rights. South Gare would add a much longer list of rare & scarce migrants I have seen there over the years.
Much more difficult to bird on site nowadays, due to partial change of ownership, health & safety etc. Wandering around site on my own is now frowned upon.
It was good whilst it lasted
Martyn