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地区之一，除城市集约化外，还经历了快速的城市扩张。这一背景为监测生物多样性对城市化的响应变化提供了理想场景，CAP长期生态研究站（CAP Long-Term Ecological Research, CAP LTER）自2000年起便采用标准化点计数协议，对GPMA及周边索诺兰沙漠区域的鸟类群落开展监测。

该CAP LTER核心监测项目的鸟类调查点包含六类通用站点分组：

1. ESCA。从CAP LTER的亚利桑那中部生态调查（Ecological Survey of Central Arizona, ESCA；前称Survey200）长期监测站点子集中选取了40个鸟类调查点。ESCA站点采用网格分层双密度（tessellation-stratified dual-density）抽样设计选址，覆盖城市、郊区、农村、商业区、公园、农田及原生索诺兰沙漠等多样化生境。此数据包早期版本包含ESCA项目中补充鸟类数据的相关信息，但鸟类调查点未必与ESCA抽样的30米×30米样地重叠，需谨慎整合两类监测数据。ESCA数据可通过CAP LTER及LTER网络数据门户获取，2016年春季调查后，15个与ESCA相关的农业、商业及访问受限站点停用，核心监测重心转向沙漠公园与PASS社区。

2. 北沙漠村（North Desert Village, NDV）。亚利桑那州立大学理工学院校园内的NDV区域是重点研究区，CAP LTER将此处小型社区景观改造为GPMA主导类型（绿洲型NDV-O、旱生型NDV-X、中生型NDV-M、对照型NDV-C、原生型NDV-N），并增设鸟类调查点。2016年春季后，该站点研究结束，监测停用。

3. 河岸生境。ESCA抽样点因随机性未覆盖占GPMA极小面积却重要的河岸生境，故专门设立12个河岸调查点，亚型包括短暂人工型（EE, n=4）、短暂自然型（EN, n=2）、永久人工型（PE, n=3）及永久自然型（PN, n=3）。2016年春季后研究完成，站点停用。

4. 盐河。盐河流经GPMA的7个站点源自盐河生物多样性项目（Salt River Biodiversity Project, SRBP），后被纳入核心监测，用于持续跟踪河岸生境鸟类状况。

5. 沙漠施肥实验（Desert Fertilization, DesFert）。2016-2017年冬季调查起，沙漠公园内6个站点被纳入核心监测，以匹配CAP LTER的DesFert实验站点。

6. 凤凰城地区社会调查（Phoenix Area Social Survey, PASS）。2016-2017年冬季调查起，原独立的PASS社区鸟类监测被整合至核心项目，保留8个旧点并新增28个点，12个PASS社区各设3个监测点。与以往仅在PASS调查前后年份访问不同，每年访问可获取更多社区鸟类种群数据。

## 方法概述

特定季节中，每个调查点由三位观鸟者独立访问，在15分钟窗口期内计数所有可见或可闻鸟类。监测频率随项目推进调整：2000年为试点年，各站点由不同数量观鸟者访问约两次；2001年起规范化为四季各三次访问；2005年减至三季；2006年起固定为春秋两季。