2018 was the single worst butterfly year since this project began. It was the only year when butterflies were at a low ebb both in numbers and diversity at BOTH high (SV,CP,DP,LC,WA) and low (RC,NS,WS,GC,SM) sites. Usually wet years are good in the mountains and bad in the Valley, and vice versa for dry years. In 2018 it was bad everywhere. So it should not be surprising if 2019 was a better year. The number of site visits held nearly constant, but the number at high elevations fell due to a late spring and meltout—partially compensated by more intense scrutiny at low elevations, especially late in the season:
The season can be tied to the strange rhythm of precipitation. The rains and snows started very late, so that in the high country there had already been freeze and desiccation damage due to the lack of snow cover before it finally materialized. But then snowfall was very heavy and persistent, yielding one of the top 5 to 10 seasonal snowfalls of record at Donner (depending on what sources one uses) and a late meltout. The early dryness would presage a poor butterfly year; the late snowiness a good one. The overwintering inocula were small due to cumulative negative population impacts still carrying over from the drought. But the two halves of the season traded off against each other, such that overall the high elevation faunas showed improvement (with some notable exceptions, documented below). At low elevations some species showed dramatic increases while others either remained low or got worse. An interesting comparison not previously made here is the maximum number of species observed in any one sample during the year:
(A longer-term compilation of this datum is available on request. Since 2002 the maxima are: SM 24 (2016); GC 37 (2004,2005); WS 22 (2005, 2016); NS 27 (2015); RC 21 (2016); WA 35 (2003); LC 42 (2013); DP 52 (2008); CP 48 (2003); SV 35 (2004). The interpretation of these data is complicated, because high numbers might reflect compression of the season due to a late/cold spring—but could also reflect larger numbers of species at or beyond the abundance threshold to be detected.)
In the Valley, the Yolo Bypass (WS) and the NS flood basins filled by midwinter and remained flooded into May. Brephidium exile and Lycaena helloides were extirpated and had very bad seasons; only one individual of L. helloides was recorded at WS in the entire year (vii.20)! Nearly all the low-elevation records of this species were at Baccharis in autumn. B. exile, wiped out at SM by flooding, was not recorded until vi.12. It peaked at a respectable 1016 on x.23 and then plummeted to 212 on xi.2, rose to 441 on xi.11, and then petered out to 2 on xii.23. Usually a Yolo Bypass flood is followed by a major midsummer rebound of the fauna, but that did not happen this year; though the number of species reached a typical high of 21, the maximum number of individuals peaked early—477 on vi.28—and was in the 200s during most of what is usually peak abundance season in autumn. NS was similar, peaking at 502 bugs on vii.7 and never exceeding 300 after viii.8. Two regionally-extinct or near-extinct species put in unexpected appearances: a Euchloe ausonides at SM on iv.22 and singletons of Pholisora catullus at NS on viii.19, ix.5 and x.18. It is known to be breeding in backyard gardens directly across the American River in Boulevard Park (a neighborhood).
For the indicator species in the Valley, phenologically it was a very late year. Of 21 species, 16 were later than in 2018 (range 1-124 days; mean 32.0 days) and 5 were earlier (range 2 to 60 days; mean 18.4 days). I included Lycaena helloides this time since it was extirpated in the Bypass both years. This again reflected the very wet late winter and delayed spring.
MIGRATORS: It was a major migration year for both the Painted Lady and the CA Tortoiseshell. 2018 had been (for whatever reason) the worst Vanessa cardui year on record in the Valley. 2019 was one of the best. We had advance warning of mass emergences and movements in late winter in southern California. The spring N-ward migration was protracted, in multiple waves. As a result breeding in the Valley was also protracted, and we had some animals all through the summer. The fall S-ward migration was sparse on both sides of the Sierra, however, and stragglers continued right through December.
The first number is the total counted up to viii.1 and the second is the number thereafter.
|Totals for year:||315,197||25,2||11250,74|
Numbers were also good in the Sierra. V. virginiensis was less common than last year.
Nymphalis californica was strong all year. Both the early-summer migration to the N and NE and the end-of-summer migration to the S and SW were in the 100s of thousands if not millions. As is often the case, we do not know where they bred in the summer—only that clouds ofthem passed over the summit of Mt. Lassen heading S. Only day-positives are recorded here:
Site 2017 2018 2019 Lang Crossing 5 6 3 Donner Pass 5 11 13 Washington 7 10 6 Sierra Valley 1 2 3 Castle Peak 5 8 8 Totals: 23 37 33
One of the more striking tortie phenomena was the abundance of the species in the Valley during the downslope autumn migration, especially at NS where it set a site record. Singletons were recorded on vii.19 , viii.18 and viii.27; then 36 on ix.25 (puddling!), 3 on x.7 and 2 on x.18. there were 6 at Gates Canyon on ix.27 but none thereafter on into winter. The Buckeye, Junonia coenia, had a better year than last but has not regained its numbers of prior years, especially during the drought. Once again it peaked in early summer, failing to produce its traditionally large autumn brood.
Last year was the worst Monarch (Danaus plexippus) year in the history of my transect—until this year.
And in the Sierra (counts, not day-positives):
|Totals (all 10 sites):||75||36||12|
For the second consecutive year, I never saw even a single wild larva! Not for not looking.
(Based on reports of breeding elsewhere, mostly S, I estimated in fall that the statewide population would increase by 2-4X. That was obviously not an extrapolation from these transect data!)
Desert immigrants were slightly more frequent than last year. Phoebis sennae: WS. V.23; SV, vi.16; Leptotes marina, SM,viii.30; NS, ix.5. A Queen was reported in Butte County (not by us!).
Other things in trouble regionally:
Satyrium sylvinus: West Sac 2017-11, 2018-2, 2019-1. North Sac 2017-107, 2018-22, 2019-35. Gates Canyon 2017-16, 2018-3, 2019-8.
Not usually recorded in Rancho—occasionally a singleton—but in 2019, 21!
Satyrium californica: Gates Canyon 2017-88, 2018-7, 2019-11. Rancho Cordova 2017-27, 2018-6, 2019-11.
Satyrium tetra: Gates 2017-7, not seen since!
Satyrium auretorum: Gates 2017-15, 2018-1, 2019-1.
Satyrium saepium: Gates 2017-5, 2018-4, 2019-5.
In the Sierra the Satyrium remained very scarce, with slight improvements at LC and SV. At SV, S. behrii recorded vi.29,vii.11 and vii.22; S. fuliginosum not seen in 2019. Euphilotes battoides, not recorded at SV in 2018, was back (v.12). E. enoptes recovered at Donner (vii.25-viii.7).
No change in status of Ochlodes yuma at Suisun.
Lycaena xanthoides: North Sac 2017-11, 2018-3, 2019-0. Suisun 2017-2, 2018-4, 2019-2.
Glaucopsyche lygdamus: North Sac 2017-5, 2018-33, 2019-3. Rancho Cordova 2017-40, 2018-18, 2019-29.
Pyrgus scriptura: West Sac 2017-48, 2018-31, 2018-15. Suisun 2017-21, 2018-8, 2019-4.
Pholisora catullus: West Sac 2017-39, 2018-12, 2019-30. North Sac 2017-1, 2018-1, 2019-3.
And now for stuff recently on the upswing!
Gates Canyon 30 15 8
In the Sierra, Oeneis ivallda returned on Castle Peak (one seen on vii.22); Neophasia menapia returned at LC and DP; Satyrium behrii and Euphilotes battoides returned at SV; and Cercyonis oetus again was not seen at CP, despite late-season forays for it. Overall, numbers of most things were up in the Sierra compared to last year, but the prognosis for next year is guarded because of the near-total failure of the summer monsoon. In the first half of summer, soil moisture was good thanks to the late snowmelt. But by late summer much of the Sierran vegetation was drought-stressed—albeit nowhere near the way it was during the drought, or in 2002. That is, the overwinter inoculum is likely to be moderate, and its survivorship will depend on the snow season. The Sierran sites that showed declines beyond 2018 were Washington and Sierra Valley. SV was disappointing nearly all season, and very droughty after July.