Phenology in Essex: lessons from the past and examples of recent trends 33
Table 2. Mean bird and insect appearance dates in Essex 1891-1927. "response" is the
number of days earlier appearance expected from a one degree Celsius warming. Mean
dates for 1999 are added for comparison.
Mean Earliest Latest response 1999
Songthrush Turdus philomelos Jan 17 Jan 1 Mar 2 - Feb 12
singing___________________________________________________________________
Swallow arrival Hirundo rustica Apr 21 Apr 10 May 14 - Apr 17
Cuckoo first heard Cuculus canorus Apr 21 Apr 6 Apr 29 2.1 Apr28
Nightingale Luscinia megarhynchos Apr 23 Apr 14 May 14 2.0 May 3
Spotted flycatcher Muscicapa striata May 21 May 7 Jun 26 - May 15
Last swallow Hirundo rustica Oct 13 Sep 1 Nov 5
Honeybee Apis mellifera Feb 26 Jan 6 Apr 3 4.6
Queen wasp Vespula, vulgaris Mar 31 Feb 14 May 28 5.1 Mar 31
Small white Pieris rapae Apr 15 Mar 26 May 9 3.8 Apr 19
Orange tip Anthocharis cardamines May 6 Apr 17 May 22 2.5 Apr 28
Meadow brown Maniola jurtina Jun 17 Apr 18 Jul 12 7.5
Table 3 summarises results from the Essex Bird Reports for the years 1964-1997. Only cuckoo and
willow warbler do not show a trend towards earliness in recent years. Perhaps population declines,
and therefore reduced opportunities for observation, in these species mask any other effects. The
trend for sand martin (Figure 4) is very marked; it is now observed more than a fortnight earlier than
in the 1960s. Five of the eight species show a significant relationship with Central England
Temperatures. Figure 5 shows the response of cuckoo to March temperature. This relationship is
statistically significant but shows more variability than the plant events mentioned above.
Table 3. Mean first arrival times of eight bird species selected from the Essex Bird Reports
1964-1997. Species are arranged in order of mean first arrival date, "response" is the number
of days earlier appearance expected from a one degree Celsius warming.
Mean Earliest Latest 1964- 1970- 1980- 1990- response
______________________________________________________1969 1979 1989 1997__________
Wheatear Oenanthe oenanthe Mar 15 Mar 2 Mar 30 Mar 17 Mar 17 Mar 15 Mar 10 3.4
Sand martin Riparia riparia_______Mar 21 Feb 29 April Mar 27 Mar 26 Mar 21 Mar 10 5.4
Willow Phylloscopus Mar 28 Mar 1 Apr 10 Mar 23 Mar 30 Mar 28 Mar 29
warbler____ trochilus__________________________________________________________________________
Swallow Hirundo rustica_______Mar 31 Mar 14 Apr 17 Apr2 Apr3 Apr 1 Mar 25 3.9
House Delichon urbica Apr5 Mar 13 Apr 19 Apr9 Apr 12 Apr2 Mar29 2.2
martin______________________________________________________________________________________
Cuckoo Cuculus canorus_______Apr 9 Mar 28 Apr 23 Apr 5 Apr 11 Apr 12 Apr 5_____3.2
Nightingale Luscinia Apr 13 Mar 20 Apr 27 Apr 15 Apr 17 Apr 10 Apr 8
__________ megarhynchos_____________________________________________________________________
Swift*_____ Apus apus___________Apr 21 Apr 2 May 2 Apr 22 Apr 24 Apr 21 Apr I fi_____-
* excluding reported event of Feb 3 1967.
Essex Naturalist (New Series) 17 (2000)