Chris Schultz

San Juan National Forest

15 Burnett Court

Durango, CO 81301

cschultz@fs.fed.us

GENERAL SPECIES INFORMATION

The Black Swift (Cypseloides niger) is a long-distance neotropical migratory bird that breeds in western North America in close association with mountain waterfalls or sea-side cliffs (Knorr 1961, Foerster 1987, Dobkin 1994). Known breeding populations are disjunct and are associated with highly specialized habitat characteristics. Black Swifts are presumed to winter in South America, but the exact range is poorly known (C. Collins pers. comm.). The most obvious threats to breeding success are developement of sea-side nesting cliffs and alteration of intermountain stream flows resulting in reduced nesting success (Colorado Natural Heritage Program 1997). The North American Breeding Bird Survey does not adequately sample the species due, in part, to its limited breeding distribution and very restricted habitat requirements, and in part to the inaccessability of its preferred breeding habitat. Partners in Flight ranks the Black Swift as a species of high priority for conservation concern (Carter et al. 1996) and, within the western U.S., as a priority species for virtually every state within its documented breeding range (Rich and Beardmore 1997). The U.S. Forest Service has designated the species as Sensitive in every agency Region in which it breeds. Colorado is estimated to host between 10% and 20% of the world’s breeding population, yet less than thirty active nesting sites are known, most on National Forest System lands. Therefore, there is a clear need for a standardized survey protocol and monitoring program that could provide data for evaluation of long-term population status and trends. This document proposes a standardized survey protocol for Black Swift nesting colonies and a conceptual method for evaluating species' status and trend.

Sampling Parameter:

I suggest the most appropriate sampling parameter for Black Swifts might be a simple count of the maximum number of individuals seen simultaneously flying about or roosting on the nesting cliff. The next logical sampling parameter, counting the number of nests in a colony, is frequently difficult due to the cryptic nature of swift nests (Knorr 1961, Farrand 1990) and the distance from the nest cliff at which many observations must be conducted. Counts of nests are also precluded at some locations, such as many sea-side cliffs, where the only accessable viewing site is on the rim. At sites where more than one annual visit can be consistently achieved, the logical parameter to track among years is the mean of the maximum daily counts. There are several benefits to conducting multiple site visits. The first benefit is the potential to place statistical parameters on estimates of colony size. The second benefit is reducing the possibility that stochastic weather events might significantly affect results of a single site visit and thus bias annual colony size estimates.

First Site Visit:

At sites that have not been previously surveyed, I recommend an initial daytime reconnaisance visit to the area. At this time, the waterfall can be evaluated for potential for Black Swift occupancy based on the criteria described by Knorr (1961 and 1993). At this time, selection of the best observation site should also be done, and that location should be marked on a USGS topographic map. Recommended trails or access routes should also be mapped for future reference. If the first site visit must occur on the day of the first survey, observers must arrive in the area with enough time to thoroughly explore all possible observation sites and area departure routes before observations are begun.

Season:

I recommend targeting colony visits to start about two weeks after eggs have hatched to avoid potentially biasing samples with the inclusion of late migrants or nonresident floating individuals (hatch date varies by site latitude and elevation, see Table 1). This problem was noted by Foerster and Collins (1990) in their analysis of swift observation data from California. Also, prior to hatch and until the young reach about 12 days of age, it is likely that one adult remains on the nest most of the time. Therefore, after about two weeks post-hatch, there is a much better chance of both adults being in sight over the colony at the same time, and thus better chance of obtaining a full colony count. Because Black Swifts are known to be a late nesting species at high elevations and northern latitudes (Knorr 1961, Hunter and Baldwin 1962), post-hatch survey visits may also provide better colony access at mountain sites due to reduced stream flows and drier trail conditions in late summer, and thus provide more consistent survey effort.

Due to the protracted nature of the Black Swift nestling period (45 days, Foerster 1987, Marin 1997), I suggest that annual survey effort should consist of three colony visits, beginning approximately two weeks after mean hatch date for that latitude, and spaced approximately two weeks apart. If only one site visit can be consistently achieved, this visit should occur approximately four to six weeks after mean hatch date. For reference in planning site visits, Table 1 provides approximate timing of Black Swift breeding events at a variety of latitudes and elevations (data is from Knorr (1961), Hunter and Baldwin (1962), Collins and Landy (1968), Collins and Foerster (1995), Marin (1997), Hirshman (1998) and personal observations.)

Reproductive Parameters:

Average clutch and brood size: 1.

Incubation period: 24-27 days with both sexes sharing duties.

Nestling period: 45 days with both sexes feeding young.

Time of Day and Weather:

Published literature (Foerster and Collins 1990) and personal experience suggests that the most productive survey time is the final two hours of daylight when chick provisioning rates may increase and adults are returning to the colony to roost. Targeting suveys for the last hours of daylight should also maximize the probability of counting local residents and might limit the potential influence on the data of non-resident foraging individuals. An important side benefit of targeting observations during the hours of hypothesized maximum swift activity is the potential for simultaneously gathering site-specific data on nest location and numbers, roost site selection, micro-habitat features, or other site-specific information which might be important to land management decisions.

All surveys should occur under relatively similar, and favorable, weather conditions. Favorable weather conditions are light winds, little to no overcast, no precipitation and seasonally moderate temperatures. Gusty onshore winds are usually present at coastal sea cliffs, and upslope winds are often found at mountain falls until just before dark and cannot be avoided. However, observations should be scheduled to avoid the passage of frontal systems or afternoon thunderstorms.

Observation Location:

An observation location should be chosen that maximizes the view of the nesting cliff and aerial access routes. This location should then be used consistently for all subsequent surveys. At mountain falls, this will often be a location near the base of the nest cliff where a clear view of the sky allows maximum ability to spot birds flying into the colony, especially in dim light conditions just before dark. At colonies where the only accessable observation sites are on the rim, choosing an observation site with the brightest possible backdrop will maximize observers ability to spot flying swifts during and after dusk.

Observers and Safety:

If at all possible, there should be two observers present at each colony visit. With two observers present, counts of flying swifts will likey be more accurate and observations of nests or roosting adults will be more complete. For consistency of sampling effort, I recommend that only two observers be used. Further, I recommend that both observers watch from the same location and not attempt to cover two viewing stations simultaneously. When surveying unoccupied habitat for new colonies, any number of additional observers will significantly increase the likelihood that swifts will be detected if they are present, and consistency of observation effort is not critical.

A second, but no less important, reason for having two observers present at each colony visit is for observer safety. Working around wet, moss-covered cliffs is inherently dangerous, especially after dark, and the presence of a second individual provides a margin of safety beyond that of a lone observer. I strongly recommend scouting departure routes during daylight hours to ensure safely exiting the area after dark, and carrying a working backup flashlight in case the first goes dead. A final safety consideration when working on cliff rims or bases is potential exposure to lightning and falling rock. Observers should always be aware of approaching thunderstorms, and take cover immediately if necessary.

Data Considerations:

This proposed survey protocol provides, at best, an estimate of the maximum number of adult Black Swifts present in suitable breeding habitat during the breeding season. A major weakness of this survey protocol is that it does not provide direct measures of nesting success or productivity. However, at those nesting colonies that are readily accessable and survey efforts are most consistent, it is logical to expect that ancillary data on nesting success and productivity will be obtained. An addtional benefit to adopting this, or any other, consistent rangewide survey protocol is the legitimate expectation of obtaining at least qualitative information about Black Swift colony persistence and metapopulation dynamics.

ACKNOWLEDGMENTS