Pollinator Observation Surveys

SOP-F611 Revision 0.2
Author

Marc Los Huertos

EA Program, Pomona College

Published

2026-06-26

1 Purpose

This SOP describes standardized methods for surveying pollinator communities at EA Program field sites using timed visual observations and passive pan traps. Pollinator surveys document the diversity and relative abundance of bees, butterflies, flies, beetles, and other flower-visiting insects, providing data for assessing habitat quality, restoration success, and the effects of land use on pollination services (Lebuhn & Fenter, 2013; Potts et al., 2010).

2 Scope

  • Applies to: Standardized pollinator observation surveys and pan trap sampling at all EA Program terrestrial field sites with flowering vegetation, including the Bernard Field Station, campus landscapes, restoration sites, and agricultural study areas
  • Does not apply to: Targeted bee nesting surveys; hive management; pollen analysis (palynology); pollinator genetics or molecular identification (though specimens collected here may be used for those purposes); aquatic insect sampling (see SOP-F610)
  • Location: All EA Program field sites with floral resources

3 Responsibilities

Role Responsibility
PI / Field Lead Approve survey design and collection permits
Trained Personnel Conduct surveys and process pan trap samples per this SOP
New Students Complete training (insect identification and sting safety) before independent work

4 Definitions

  • Diel activity pattern: The temporal distribution of an organism’s activity across a 24-hour period; most bee species are diurnal with peak activity between 09:00 and 15:00 under sunny, warm conditions; surveys outside peak activity hours systematically underestimate community richness (Lebuhn & Fenter, 2013).
  • Floral density: The number of open flowers per unit area at a survey location; a key covariate for pollinator abundance because visitation scales with resource availability; estimated visually as flowers per m2 or as qualitative categories (low, medium, high) at each survey event.
  • Focal flower observation: A survey method in which a single flowering plant or patch is observed for a fixed duration (typically 10 minutes) and all pollinators visiting any flower during that period are recorded; useful for comparing visitation rates between plant species or treatments (Westphal et al., 2008).
  • Functional group: A coarse taxon category used when species-level identification is not possible in the field; the EA Program uses 10 groups: honey bee (HB), bumble bee (BB), small native bee (SB), large native bee (LB), butterfly (BF), syrphid fly (SF), other fly (OF), beetle (BT), wasp (WA), and other (OT).
  • Independent detection event: A single detection of a pollinator at a flower, counted only once per survey period regardless of how long the individual remains; used to standardize counts across surveys of different duration.
  • Pan trap: A colored bowl (white, fluorescent yellow, fluorescent blue) filled with soapy water; passively captures flying insects attracted by color resemblance to flowers; effective for small- to medium-sized bees but under-represents large-bodied bees and butterflies (Lebuhn & Fenter, 2013; Westphal et al., 2008).
  • Pollinator: Any animal that moves pollen from the anther to the stigma of a flower, facilitating plant reproduction; includes bees, flies, butterflies and moths, beetles, and hummingbirds; bees are the dominant pollinators at most EA Program field sites (Potts et al., 2010).
  • Pollination service: An ecosystem service provided by flower-visiting animals; essential for reproduction of approximately 75% of flowering plant species and 35% of global food crop production (Potts et al., 2010).
  • Timed observation transect: A standardized survey in which the observer walks a fixed route (typically 50 m x 2 m) at a standardized pace (approximately 10 m per minute) and records all pollinators observed on flowers within the survey corridor; produces a count-based estimate of relative pollinator activity (Dicks et al., 2016; Lebuhn & Fenter, 2013).
  • Voucher specimen: A preserved insect specimen deposited in a reference collection to document the occurrence of a species at a site; required for any first records and difficult identifications; pinned through the right mesopleuron following standard entomological practice.

5 Safety and Hazards

WarningHazards
  • Biological: Bee and wasp stings are the primary hazard. Personnel with known Hymenoptera allergies must carry a prescribed epinephrine auto-injector (EpiPen) and inform the field lead before every outing. Africanized honey bees may be present at some Southern California sites.
  • Chemical: Soapy water in pan traps (low risk). Ethanol (70%) used for specimen preservation is flammable.
  • Physical: Heat exposure during mid-day surveys. Uneven terrain. Pan traps may be trampled by people or wildlife.

5.1 Required PPE

5.2 Permits

Insect collection may require a Scientific Collecting Permit from CDFW depending on the site and target taxa. No permit is needed for observation-only surveys.

5.3 Emergency Procedures

For anaphylactic reactions: administer EpiPen, call 911. Refer to SOP-F001 Field Safety. If encountering an aggressive swarm, walk calmly away; do not swat or run erratically.

6 Equipment and Materials

6.1 Timed Observations

Item Notes
Stopwatch or phone timer For standardizing observation periods
Hand lens or magnifying glass For in situ identification
Camera (macro-capable or phone) For photo-documenting pollinators
Field data sheet Pre-printed from Appendix A
Insect field guide e.g., California Bees and Blooms
iNaturalist app (smartphone) For photo-based identification; see SOP-F602
Compass and GPS For recording transect or plot locations

6.2 Pan Traps

Item Notes
Plastic bowls (12 oz, 3.25 in rim) White, fluorescent blue, and fluorescent yellow; one of each color per station
Fluorescent spray paint (blue, yellow) For painting white bowls; use UV-bright paints
Unscented liquid dish soap 2–3 drops per bowl (breaks surface tension)
Water To fill bowls approximately 2/3 full
Wooden stakes or wire stands For elevating bowls to canopy height in tall vegetation
Fine mesh strainer For removing insects from bowls
Whirl-Pak bags or vials For storing collected specimens
70% ethanol For preserving specimens
Forceps (soft-tipped) For handling specimens
Labels (waterproof, internal) For vial and bag identification

7 Procedure

7.1 Survey Timing and Conditions

Conduct pollinator surveys during peak pollinator activity:

  • Time of day: 09:00–15:00 local time (peak flight activity)
  • Weather: Sunny to partly cloudy; wind speed below Beaufort 4 (< 5.5 m/s); temperature above 15 C. Do not survey during rain, heavy overcast, or high winds, as pollinator activity drops sharply.
  • Season: During peak bloom at the study site. In Southern California, this is typically March through June for most habitats, with a secondary bloom in fall for some species.
  • Flowering requirement: Surveys are only meaningful when flowers are present. Record the dominant flowering species and estimate floral density (flowers per m2) at each survey location.

7.2 Method A: Timed Observation Surveys

Timed observations record pollinator visits to flowers along a fixed route or within a fixed plot during a standardized time period (Dicks et al., 2016; Lebuhn & Fenter, 2013).

Transect walk method:

  1. Establish a transect (typically 50 m x 2 m, or a 100 m x 1 m corridor) through the area of interest. Record the transect coordinates per SOP-F006.
  2. Walk the transect slowly at a pace of approximately 10 m per minute.
  3. Record every pollinator observed visiting a flower within the 2 m band on either side of the transect center line (or 1 m on each side for a 2 m wide transect).
  4. For each observation, record:
    • Pollinator group or species (see Section 6.4)
    • Flower species being visited
    • Behavior (nectaring, pollen collecting, resting)
    • Time of observation
  5. Complete the transect in 10–15 minutes. Do not stop and wait for pollinators; maintain a steady pace.
  6. Repeat the transect 2–3 times per sampling event, spaced at least 30 minutes apart.

Focal flower observation method:

  1. Select a flowering plant or patch and observe for a fixed period (typically 10 minutes).
  2. Record every pollinator that visits any flower on the focal plant during the observation period.
  3. This method is useful for comparing visitation rates among plant species or treatments.

7.3 Method B: Pan Trap Sampling

Pan traps passively capture flying insects attracted to colored bowls (Lebuhn & Fenter, 2013; Westphal et al., 2008).

  1. At each sampling station, set out three bowls: one white, one fluorescent blue, one fluorescent yellow. Space bowls approximately 3 m apart.
  2. Fill each bowl approximately 2/3 full with water. Add 2–3 drops of unscented dish soap (this breaks the surface tension so insects sink).
  3. Place bowls at the height of the surrounding vegetation canopy:
    • In short grass or bare ground: set directly on the ground
    • In tall vegetation (> 30 cm): elevate on stakes or wire stands so the bowl rim is at canopy height
  4. Deploy traps in the morning (by 09:00) and retrieve after 24 hours. For shorter deployments (4–6 hours), retrieve in the afternoon.
  5. Pour the contents of each bowl through a fine mesh strainer. Transfer captured insects to a labeled Whirl-Pak bag or vial with 70% ethanol.
  6. Label each vial with: site, station number, bowl color, date deployed, date retrieved, and collector initials.
  7. Return specimens to the lab for sorting, pinning, and identification.
Note

Pan traps are biased toward small- to medium-sized bees and may under-represent large-bodied bees (bumble bees) and butterflies (Westphal et al., 2008). Combine pan traps with timed observations for a more complete picture of the pollinator community.

7.4 Pollinator Identification

Identify pollinators to the finest taxonomic level possible in the field. At a minimum, assign each observation to one of the following functional groups:

Code Group Examples
HB Honey bee Apis mellifera
BB Bumble bee Bombus spp.
SB Small native bee Halictus, Lasioglossum, Ceratina
LB Large native bee Xylocopa, Megachile
BF Butterfly All Lepidoptera
SF Syrphid fly (hover fly) Syrphidae
OF Other fly Bombyliidae, Tachinidae, etc.
BT Beetle Flower-visiting Coleoptera
WA Wasp Vespidae, Sphecidae, etc.
OT Other Hummingbirds, moths, ants

Photograph all specimens that cannot be identified in the field. Upload photos to iNaturalist per SOP-F602 for community-assisted identification.

7.5 Specimen Processing (Lab)

  1. Sort pan trap specimens by order under a dissecting scope.
  2. Pin bee specimens following standard entomological practice (pin through the right mesopleuron) and label with locality, date, collector, and determination.
  3. Store pinned specimens in a labeled unit tray in the insect collection.
  4. Specimens can be submitted to a taxonomic specialist or DNA barcoded (COI) for species confirmation.

8 Quality Control

  • Record weather conditions (temperature, wind, cloud cover) at the start and end of every survey. Do not compare data collected under different weather conditions without accounting for detectability.
  • On 10% of surveys, have two observers independently record pollinators on the same transect to assess inter-observer agreement.
  • Record floral density and dominant flowering species at every survey; pollinator abundance is strongly influenced by floral resource availability.
  • For pan traps, inspect bowls mid-deployment if wind or wildlife disturbance is likely. Refill or replace tipped bowls and note the interruption.
  • Voucher-pin at least 5 representative specimens per functional group per site per season for the reference collection.

9 References

Dicks, L. V., Viana, B., Bommarco, R., Brosi, B., Arizmendi, M. del C., Cunningham, S. A., Galetto, L., Hill, R., Lopes, A. V., Pires, C., et al. (2016). Ten policies for pollinators. Science, 354(6315), 975–976. https://doi.org/10.1126/science.aai9226
Lebuhn, G., & Fenter, N. (2013). Field guide to the common bees of California: Including bees of the Western United States. University of California Press.
Potts, S. G., Biesmeijer, J. C., Kremen, C., Neumann, P., Schweiger, O., & Kunin, W. E. (2010). Global pollinator declines: Trends, impacts and drivers. Trends in Ecology and Evolution, 25(6), 345–353. https://doi.org/10.1016/j.tree.2010.01.007
Westphal, C., Bommarco, R., Carre, G., Lamborn, E., Morison, N., Petanidou, T., Potts, S. G., Roberts, S. P. M., Szentgyorgyi, H., Tscheulin, T., Vaissiere, B. E., Woyciechowski, M., Biesmeijer, J. C., Kunin, W. E., Settele, J., & Steffan-Dewenter, I. (2008). Measuring bee diversity in different European habitats and biogeographical regions. Ecological Monographs, 78(4), 653–671. https://doi.org/10.1890/07-1292.1

11 Training Record

Before conducting pollinator surveys independently, personnel must:

  1. Read this SOP and SOP-F001 Field Safety in full
  2. Disclose any Hymenoptera allergy to the field lead and carry an EpiPen if prescribed
  3. Demonstrate identification of the 10 pollinator functional groups (Section 6.4) using pinned specimens or photographs
  4. Participate in a supervised transect observation survey and pan trap deployment
  5. Be signed off by the PI or field lead

12 Appendix A: Pollinator Observation Data Sheet

Site: _______________ Transect ID: ____________ Date: ___________

Observer: _____________ Start time: ______ End time: ______

Weather: Temp: ___ C Wind (Beaufort): ___ Cloud: ___ % Sun: Y / N

Dominant flowering species: __________________________________

Time Pollinator Group/Species Flower Species Behavior Photo #