Point-count bird censusing: long-term monitoring of bird abundance and diversity in central Arizona-Phoenix, ongoing since 2000

## project overview

Over the past half-century, the greater Phoenix metropolitan area (GPMA)
has been one of the fastest growing regions in the US, experiencing
rapid urban expansion in addition to urban intensification. This
backdrop provides an ideal setting to monitor biodiversity changes in
response to urbanization, and the CAP LTER has been using a standardized
point-count protocol to monitor the bird community in the GPMA and
surrounding Sonoran desert region since 2000.

The bird survey locations in this CAP LTER core monitoring program
include six general site groupings:

1. ESCA. Forty bird survey locations were selected from a subset of the
CAP LTER's Ecological Survey of Central Arizona (ESCA; formerly
named Survey200) long-term monitoring sites. ESCA sites were located
using a tessellation-stratified dual-density sampling design, and,
as such, span a diversity of habitats including urban, suburban,
rural, commercial areas, parks, agricultural fields, and native
Sonoran desert. Earlier versions of this data package included data
from the ESCA project that was intended to complement the bird data.
However, while positioned in close proximity, the bird survey
locations do not necessarily overlap with the 30m x 30m plot that
constitutes an ESCA sampling location, and leveraging data from
these two monitoring programs should be addressed carefully. ESCA
data have corresponding survey location names, and those data are
available through the CAP LTER and LTER network data portals. At the
conclusion of the 2016 spring survey, fifteen of the ESCA-correlated
sites were discontinued as the core monitoring program refocused its
efforts on desert parks and PASS neighborhoods. Among the deleted
locations were all agricultural and commercial sites, as well as
sites where access had become restrictive.

2. North Desert Village (NDV). Additional bird survey locations were
positioned in treatment areas of the North Desert Village (NDV).
This was a site of intense study on the Arizona State University
Polytechnic Campus in which the CAP LTER converted the landscaping
of small neighborhoods to reflect the dominant landscaping
preferences employed throughout the GPMA. NDV landscape types
include: oasis (NDV-O), xeric (NDV-X), mesic (NDV-M), control
(NDV-C), and native (NDV-N). Monitoring at NDV was discontinued
after the spring 2016 season as research efforts at this site came
to an end.

3. Riparian. While the forty bird survey locations that were selected
to coincide with ESCA sampling locations span a wide diversity of
habitats throughout the GPMA, because of the generally random nature
of selecting those sites, they did not reflect riparian habitats.
Riparian areas are important bird habitat but constitute a very
small area of the GPMA. To address this deficiency, bird survey
locations were established specifically in twelve riparian habitats.
Riparian habitat sub-types include: (1) ephemeral-engineered (EE,
n=4), (2) ephemeral-natural (EN, n=2), (3) perennial-engineered (PE,
n=3), and (4) perennial-natural (PN, n=3). This research was
successfully concluded and these sites were discontinued after the
spring 2016 season.

4. Salt River. Seven study sites along the Salt River as it runs
through the GPMA that were selected as part of a related study (Salt
River Biodiversity Project (SRBP)) were ultimately included in the
CAP LTER's core bird monitoring programs. These sites reflect
continued monitoring of riparian habitat.

5. Desert Fertilization. Beginning with the 2016-2017 winter survey,
six sites at desert parks were added to core monitoring to coincide
with the CAP LTER Desert Fertilization (DesFert) experiment sites.

6. PASS. Beginning with the 2016-2017 winter survey, what used to be a
separate bird-monitoring effort (monitoring in Phoenix Area Social
Survey (PASS) neighborhoods) was incorporated into this core
bird-monitoring program. Eight points were carried over from prior
PASS monitoring, and 28 new points established, resulting in three
bird monitoring locations in each of the twelve PASS neighborhoods.
Visiting these locations each year, versus only in years surrounding
the PASS survey as done previously, provides more data on bird
populations found in the neighborhoods of the CAP LTER study area.

## method overview

In a given season, each bird survey location is visited independently by
three birders who count all birds seen or heard within a 15-minute
window. The frequency of surveys has varied through the life of the
project. The first year of the project (2000) was generally a pilot year
in which each site was visited approximately twice by a varying number
of birders. The monitoring became more formalized beginning in 2001, and
each site was visited in each of four seasons by three birders. The
frequency of visits was reduced to three seasons in 2005, and to two
season (spring, winter) beginning in 2006.

项目概述

过去半个世纪以来，大凤凰城都会区（greater Phoenix metropolitan area, GPMA）一直是美国增长最快的区域之一，经历了快速的城市扩张与城市集约化发展。这一背景为监测城市化响应下的生物多样性变化提供了理想的研究场景。自2000年起，CAP长期生态研究站（CAP LTER）便采用标准化的点计数规程，对大凤凰城都会区及周边索诺兰沙漠区域的鸟类群落进行监测。

本CAP LTER核心监测项目的鸟类调查点位共分为六大类群：

1. 亚利桑那州中部生态调查（Ecological Survey of Central Arizona, ESCA，前身为Survey200）：从CAP LTER的亚利桑那州中部生态调查长期监测站点子集中共选取40个鸟类调查点位。ESCA站点采用镶嵌分层双密度抽样设计布设，涵盖城市、郊区、乡村、商业区、公园、农田以及原生索诺兰沙漠等多样生境。本数据包的早期版本曾包含用于辅助鸟类调查的ESCA项目数据，但尽管两类监测点位地理位置相近，鸟类调查点位与作为ESCA抽样单元的30米×30米样地未必重合，因此在整合两类监测项目的数据时需谨慎处理。ESCA数据带有对应的调查点位名称，可通过CAP LTER及长期生态研究网络（LTER Network）的数据门户获取。2016年春季调查结束后，随着核心监测项目将重点调整至沙漠公园与PASS社区，15个与ESCA关联的监测点位被停用。被停用的点位涵盖全部农业与商业类站点，以及无法再获取通行权限的站点。

2. 北沙漠村落（North Desert Village, NDV）：额外的鸟类调查点位布设于亚利桑那州立大学理工学院校区内的北沙漠村落（NDV）处理区域。该站点是一项密集研究的场地：CAP LTER将小型社区的景观改造为匹配大凤凰城都会区主流景观偏好的类型。NDV的景观类型包括：绿洲型（NDV-O）、旱生型（NDV-X）、湿生型（NDV-M）、对照型（NDV-C）以及原生型（NDV-N）。2016年春季季末调查结束后，随着该站点的研究工作收尾，NDV的监测工作随之终止。

3. 河岸生境：此前选取的与ESCA抽样点位匹配的40个鸟类调查点位虽覆盖大凤凰城都会区多样生境，但由于点位选取整体偏向随机，未能涵盖河岸生境。河岸生境是重要的鸟类栖息生境，但在大凤凰城都会区内占比极低。为弥补这一缺陷，研究团队专门在12个河岸生境中布设了鸟类调查点位。河岸生境亚型包括：（1）临时人工型（ephemeral-engineered, EE, n=4）、（2）临时自然型（ephemeral-natural, EN, n=2）、（3）永久人工型（perennial-engineered, PE, n=3）以及（4）永久自然型（perennial-natural, PN, n=3）。该研究已于2016年春季季末顺利结束，相关监测点位随之停用。

4. 盐河：作为相关研究「盐河生物多样性项目（Salt River Biodiversity Project, SRBP）」的一部分，沿流经大凤凰城都会区的盐河选取的7个研究站点，最终被纳入CAP LTER的核心鸟类监测项目。这些站点用于持续监测河岸生境。

5. 沙漠施肥实验（Desert Fertilization, DesFert）：自2016-2017年冬季调查起，核心监测项目新增了6个位于沙漠公园的站点，与CAP LTER的沙漠施肥实验（DesFert）站点相匹配。

6. PASS：自2016-2017年冬季调查起，原本独立开展的鸟类监测工作——菲尼克斯地区社会调查（Phoenix Area Social Survey, PASS）社区鸟类监测——被纳入本核心鸟类监测项目。原PASS监测项目保留了8个监测点位，并新增28个点位，最终在12个PASS社区中各设置3个鸟类监测点位。与此前仅在PASS调查前后年份开展监测的方式不同，每年对这些点位进行监测，可为研究区域内社区的鸟类种群提供更丰富的观测数据。

方法概述

在每个调查季中，每名鸟类调查员独立对每个鸟类调查点位开展一次调查，在15分钟的窗口期内记录所有目视或听闻所见的鸟类。项目开展期间，调查频次经历了多次调整。项目首年（2000年）为试点阶段，各站点约被调查2次，参与调查的鸟类调查员人数不固定。2001年起监测工作趋于规范化，每个站点在四个季节中各由三名鸟类调查员开展一次调查。2005年调查频次缩减为每年三个季节，2006年起调整为每年两个季节（春季、冬季）。