5 year species totals breakdown

I decided to do some analysis of all the species that have occurred in 5 year blocks and whilst I can't show the excel file that reveals the specifics, the numbers are as follows;

1980 - 1984 : 166 Species
1985 - 1989 : 170 Species
1990 - 1994 : 154 Species
1995 - 1999 : 147 Species
2000 - 2004 : 159 Species
2005 - 2009 : 155 Species
2010 - 2014 : 169 Species

With the new website coming very soon now, I'll try and find a away of showing the species involved, but it is fair to say from 1995 to 1999, it was either a drought, or the site wasn't comprehensively watched...I think it was the latter.

A few things stands out -

There are no passage raptors prior to 2000 (other than Osprey)

There are no records of :

Any divers since 1987
Red-necked Grebe since 1999
Shag since 1994
Whiter-fronted Goose since 2002
Brent Goose since 1993
Red Breasted Merganser since 1990
Sanderling since 1998
Little Stint since 1993
Temminck's Stint since 1993
Turtle Dove since 2002 (possibles reported heard only 2004 & 2009)
Water Pipit since 1987
Tree Pipit since 1989 (except for 2011 & 2014 autumn records)
Ring Ouzel since 1988
Marsh Tit since 1990 (I doubt the 1998 & 1992 records as both are in May)
Willow Tit since 1990 (I doubt the 1995 & 1995 records in June & July)
Tree Sparrow since 1988
Corn Bunting since 2003 (dubious records claimed April 1999 & June 1998, genuine records 1985 & 1983)

Of sad note there are only 3 records of Yellowhammer since 2005.

The modern species additional species -

Bittern (regularly from 1995, then every year since 2002)
Little Egret records began 2000 (1st record 1996)
Red Kite records began 2001
Marsh Harrier began 2000

Peregrine began 1998 (annual since 2003)

Barn Owl records began 2001 (1st & 2nd records 1981 & 1990)

Ring-necked Parakeet records began 2002
Cetti's Warbler annual from 2003 (1st & 2nd records 1984 & 1992)
Raven annual from 2005

There are a few more things to talk about another time